The main opposition party in Zambia has filed a court petition against the re-election of President Edgar Lungu.
The United Party for National Development alleges the poll on 11 August was rigged and wants a recount.
Mr Lungu was due to be sworn in next Tuesday after securing 50.35% of the vote, avoiding a second round.
But according to Zambia's constitution, any inauguration has to be delayed until the Constitutional Court rules on the case.
Zambia's election commission has insisted that the poll was free and fair.
But it also described the level of political violence ahead of the elections as unprecedented.
It was forced to suspend campaigning in the capital, Lusaka, for 10 days because of the unrest.
Opposition candidate Hakainde Hichelema, who took 47,6% of the vote, told the BBC's Focus on Africa radio programme that the election was stolen from him and did not reflect the will of the people.
"The first respondent did not receive more than 50% of the total votes cast. The voter register was not credible and its non-availability before the elections compromised the transparency of the electoral process," Reuters news agency quotes the petition as saying.
The Constitutional Court has two weeks to rule on the petition.
Zambia's election rivals:
Edgar Lungu - Patriotic Front (PF)
- The 59-year-old lawyer became president in January 2015 in an election called after the death in office of President Michael Sata
- He served in Mr Sata's government as minister for justice and defence
- Support base: Home area of Eastern province, the capital, Lusaka, and the Copperbelt plus the Bemba-speaking regions
- Known for ordering a national day of prayer last year to help combat the economic problems facing the country
- Married with six children, this election has been seen as a personal referendum on him
Hakainde Hichilema - United Party for National Development (UPND)
- The 54-year-old economist has contested nearly all elections in Zambia since 2006
- A wealthy businessman, he has a solid track record in the private sector
- Support base: Home region of Southern Province and is popular with younger voters
- Known for being Zambia's second largest cattle rancher
- Commonly referred to by his initials HH, he is married with three children