Gunfire was heard on Friday in Guinea's capital Conakry as supporters of opposition presidential candidate Cellou Dalein Diallo clashed with police, witnesses are quoted as saying to Reuters news agency.
"There were warning shots. The police intervened to clear
the barricades and disperse the demonstrators," Oumar Camara, a
local resident, is quoted as saying to Reuters.
It comes after the election commission released preliminary results of Sunday's presidential vote from 37 of the 38 districts.
Those results show the incumbent Alpha Condé won around twice as many votes as Mr Diallo.
Mr Diallo has complained of large-scale fraud and declared himself the winner.
The government has ordered the army to restore order following violent protests over the election results.
At least nine people have died in the latest violence.
Guinea's Condé set for victory in preliminary results
BBC World Service
Preliminary results of Sunday's presidential election in Guinea indicate that the President, Alpha Condé, appears set for a first round victory.
The election commission released fresh results late on Thursday which showed the 82-year-old president to be the clear leader in the race.
He has a lead of 1.2 million votes with 37 of 38 electoral districts counted, Reuters news agency reports.
But the main opposition candidate, Cellou Dalein Diallo, has complained of large-scale fraud and has declared himself the winner.
There has been widespread violence in Guinea since the election and after President Condé's controversial decision earlier this year to seek a third term, which required a change to the constitution.
At least 10 dead in Guinea post-election violence
At least 10 people have died in post-election violence in Guinea, according to the country's security minister.
President Alpha Condé is currently leading according to results from the 14 constituencies announced by the electoral commission so far, Reuters news agency reports. There are 20 constituencies in all.
His challenger Cellou Dalein Diallou claimed victory and said the election was marred by "anomalies".
He accused President Condé's administration of modifying results in the incumbent's favour.
President Condé has called for calm as the country awaits the official election results.
His controversial bid for a third term had led to protests before the elections during which at least 50 people died, according to Amnesty International.
Guinea's government has condemned the spread of "fake news" online following the first round of Guinea's presidential elections on Sunday.
Minister of Foreign Affairs Mamadi Touré denounced as "completely false" a video circulating online claiming to be a recording of a phone call made by President Alpha Condé conceding defeat to his rival Cellou Dalein Diallo.
He dismissed another viral post claiming that diplomats were putting pressure on President Condé "to accept defeat and that he was trying to "negotiate a second round to avoid humiliation in the first round".
Official results have not yet been announced, despite a declaration of victory by opposition leader Cellou Dalein Diallo on Monday.
Guinea's electoral commission said it was the only body authorised to declare the results.
Ballots are being counted in Guinea's presidential election as incumbent, 82-year-old Alpha Condé, seeks a controversial third term.
Provisional results must be announced 72 hours after closure of polling stations, according to the electoral law.
Candidates will then have eight days to lodge appeals, failure to which the final results will be deemed uncontested.
Presidential candidates need more than 50% of the vote for an outright victory, or there will be a second round on 24 November.
Ten other candidates are also running.
Sunday's election was conducted in a tense atmosphere although Security Minister, Damantang Camara said no major incidents were registered.
He said he was concerned by a statement from the leader of the opposition Union of Democratic Forces of Guinea (UFDG) party, Cellou Dalein Diallo, who said he would not recognise the results if he would not win.
He urged candidates to refrain from making irresponsible
Hundreds of people in Kankan city in eastern Guinea have fled their homes as tension rises before Sunday's presidential election in which Alpha Condé is seeking a controversial third term.
It follows violent clashes in the city between his supporters and those of opposition UFDG candidate Cellou Dalein Diallo, who had planned to visit the area.
Kankan is a ruling party stronghold but the wider region is also home to many Fulani people - the same community Mr Diallo hails from, reports BBC Afrique's Lalla Sy.
Our reporter says the latest violence appears to be a reprisal for an attack by angry youths on the motorcade of Guinea's Prime Minister Kassory Fofana, who had campaigned in the UFDG stronghold of Labé a fortnight ago.
Some 30 people were injured in that attack and damage to property was reported.
The UN has warned that continued invoking of ethnic affiliations and hate speech in Guinea's election campaigns could lead to violence.
The UN rights boss Michelle Bachelet and acting Special Adviser on the Prevention of Genocide Pramila Patten have urged candidates to refrain from hate speech.
"There have been increasingly pervasive and divisive appeals to ethnic affiliations during the campaign, particularly references to the Malinké and Peuhl ethnicities," a joint statement read in part.
President Alpha Condé, who is seeking a controversial third term, is largely backed by Malinké people, while his main opponent, Cellou Dalein Diallo, is largely backed by Fulani people, although both insist that they are pluralist, AFP news agency reports.
Guinea is set to hold presidential elections on 18 October.
So far, at least 50 people have been killed during demonstrations against President Condé's third term bid, according to Amnesty International.
At least 50 people killed in Guinea protests - Amnesty
BBC World Service
The human rights organisation Amnesty International says at least 50 people have been killed, mostly shot dead, in Guinea during protests in the last year.
Most of these protesters were killed during demonstrations against a third term for President Alpha Condé.
In a new report, Amnesty accuses defence and security forces of being responsible for the killings and says they are acting with impunity.
The report also documents 200 people who were injured during protests and 70 arbitrary detentions.
Amnesty called on the authorities to investigate and prosecute those responsible.
Presidential elections in Guinea are due later this month
Guinea opposition leader's home 'blocked' amid protests
The world through its media
The authorities in Guinea have cordoned
off the home of one of the leaders of the opposition National Front for the Defence
of the Constitution (FNDC), the party has said.
The FNDC says in a Facebook post
that the access to the home of its national coordinator, Abdourahamane Sano, has
been closed off by the police.
This comes ahead of planned protests on Tuesday against President Alpha Conde's bid for a third term in October's election.
The FNDC, an alliance of civil society groups and opposition parties, has rejected Mr Conde's candidacy and vowed that the protests will take place despite a government ban.
"Fearing the magnitude of citizen mobilisation for the FNDC march, which is planned for the Fidel Castro Motorway on 29 September, Alpha Conde has taken the decision to prohibit this demonstration against his third mandate," the alliance said.
Although the FNDC had called for boycott of the polls, at least 11 opposition candidates will face off against 82-year-old Conde in the 18 October election.
The latest round of protests will be a key test of the FNDC's mobilising power after the group parted ways with several allied political parties over their participation in the presidential election.
Guinea's top court clears Condé third term bid
Getty ImagesCopyright: Getty Images
Guinea's constitutional court, the highest in the West African country, has approved 82-year-old President Alpha Condé's bid for a third term in next month's election.
The court also approved 11 other candidates, including the main opposition challenger Cellou Dalein Diallo.
There have been months of protests against Mr Condé's re-election bid after he pushed through a constitutional change in a referendum in March which allowed him to stand for a third term.
At least 30 people are reported to have died in the protests.
Mr Condé was first elected in 2010 and then re-elected in 2015.
On Tuesday, Nigeria's President Muhammadu Buhari called on West African leaders to stick to their constitutional term limits - which he described as a source of crisis and political tension in the region.
Buhari condemns third-term bids by West African leaders
BBC News, Lagos
Nigeria's President Muhammadu Buhari has called on West African leaders to stick to their constitutional term limits.
"It is important that as leaders of our individual member states of Ecowas, we need to adhere to the constitutional provisions of our countries, particularly on term limits. This is one area that generates crisis and political tension in our sub-region," he said.
The comments follow decisions by Ivory Coast's President Alassane Ouattara and Guinea's President Alpha Condé to run for third terms in their respective countries.
President Buhari’s comments were made during an in-person summit of leaders of the regional bloc, the Economic Community of West African States (Ecowas), held in Niamey, the capital of Niger.
President Ouattara's decision to run for a third term following the sudden death of his preferred successor triggered protests in Ivory Coast. His critics say the move is unconstitutional.
Violent protests have also been witnessed in neighbouring Guinea where 82-year-old President Alpha Condé is seeking a controversial third term in October.
The one-day Ecowas summit on Monday was attended by eight heads of state, including the presidents of Ghana, Senegal and Burkina Faso.
Other topics covered included the ongoing political crisis in Mali. The leaders called for a swift transition to civilian rule in the country following a military coup on 18 August.
The regional bloc has already imposed sanctions on Mali and asked for elections to take place within a year.
Meanwhile Mali's toppled President Ibrahim Boubacar Keïta flew out late on Saturday for treatment in the United Arab Emirates.
The junta said Mr Keïta must return to Mali in the next three months after receiving medical treatment abroad - a time-limit it said was agreed with Ecowas.
This was the first in-person regional summit in more than six months. West African leaders have been meeting virtually in the wake of the coronavirus pandemic.