Yemen President Ali Abdullah Saleh returns to Sanaa
Yemen's President Ali Abdullah Saleh has returned to the country from Saudi Arabia three months after surviving an assassination attempt.
Yemen TV said President Saleh arrived in the capital, Sanaa, by private plane at dawn.
Hours after his arrival, a presidential official said Mr Saleh was calling for a "truce and a ceasefire".
He went to Saudi Arabia in June for treatment following a rocket attack on the grounds of the presidential palace.
President Saleh, who has been in power for more than 30 years, has faced months of protests urging him to quit.
Correspondents say his return raises the risk of all-out civil war.
"The president calls on all political and military parties to achieve a truce," said the official, quoted by AFP news agency.
"There is no alternative to dialogue and negotiations to end the bloodshed," he added.
Later, the US urged President Saleh to begin a transfer of power and arrange presidential elections.
The surprise return of President Saleh raises the stakes in Yemen.
When he left the country for Saudi Arabia, opposition activists hoped he would be forced to step down. But he has so far resisted domestic and foreign pressure to resign.
His presence in Yemen is likely to strengthen his supporters and it increases fears among his opponents of an escalation in fighting.
In recent days there has been a surge in violence between forces loyal to President Saleh and rival opposition factions.
There are fears that if the violence continues, the country could slip into civil war.
In the south, there are concerns that Islamist militants linked to al-Qaeda are taking advantage of the turmoil in the country, stepping up attacks on government forces there.
"The Yemeni people have suffered enough and deserve a path towards a better future," White House spokesman Jay Carney said.
In Sanaa, anti-government protesters and supporters of President Saleh held rallies after Friday prayers.
An al-Jazeera correspondent in the city says they have taken place within a few miles of each other, although it appeared many anti-government protesters had stayed at home for fear of violence.
Protest organiser Mohammed al-Asl said Mr Saleh's return would lead to "an escalation of violence".
"But let him come back - we want him to come back and be tried for his crimes," he added.
Activists have been camped out in an area of Sanaa dubbed Change Square since January, demanding an end to President Saleh's rule.
Clashes in the capital have recently intensified as elite Republican Guards, led by President Saleh's son Ahmed, fight running battles with army units that have defected to the opposition and tribal fighters who support the protesters.
More than 80 people, mostly unarmed protesters, have been killed since Sunday.
Doctors say at least one person was killed overnight and many others wounded when mortars landed in Change Square. Other reports said four people were killed in the northern al-Hasaba district on Friday.
Correspondents in Sanaa reported a surge in artillery and machine-gun fire as news of President Saleh's return broke. As least some of the gunfire was celebratory, they said.
Yemeni state TV broadcast old footage of Mr Saleh and played national songs as it reported his return.
- 27 Jan: Thousands take to the streets in Sanaa and southern cities urging President Saleh to quit; weeks of mass protests follow
- 18 Mar: 52 protesters killed by snipers; Mr Saleh declares state of emergency
- 21 Mar: Several senior army commanders defect to protesters
- 23 Apr: Mr Saleh says he will stand down within weeks; he later appears to renege on deal
- 24 May: Clashes erupt between Saleh loyalists and tribal groups; dozens die in days of fighting
- 3 Jun: Shells hit presidential compound, injuring Mr Saleh; he leaves country for treatment
- 18 Sep: Government forces launch crackdown on protester camps; more than 80 die in five days
- 23 Sep: President Saleh returns to Yemen
Protest leader Abdel-Hadi al-Azizi said President Saleh's return "means more divisions, more escalation and confrontations".
"We are in a very critical escalation," he told AP news agency.
Hopes of a lasting ceasefire to enable a reform process to take place in which President Saleh would yield power are fading.
On Tuesday the government agreed a truce following negotiations with Western envoys. However, the ceasefire broke down hours later.
The UN High Commissioner for Human Rights, Navi Pillay, warned on Thursday that Yemen was at a "dangerous crossroads".
Gulf Co-operation Council (GCC) chief Abdulatif al-Zayani visited Yemen on Tuesday to try to broker a deal to the crisis but left the next day empty-handed.