Opposition candidate Joseph Boakai has maintained a slim lead in the Liberian presidential election after official results from more than 99% of polling stations were announced.

The 78-year-old political veteran has 50.89% of the votes, while incumbent President George Weah has 49.11%.

That represents a lead of more than 28,000 votes, with nearly all the ballots accounted for.

The latest results have sparked celebrations in the capital, Monrovia.

Mr Boakai's supporters have been gathering at his party's headquarters in the city, convinced that he has won the election.

They have been shouting for President Weah, who has served one term, to go - and chanting "we beat the Buga dancer", referring to a song that became associated with his campaign.

There have been no formal statements from either of the candidates.

The electoral commission says that it has announced the results from 99.58% of the polling stations following Tuesday's run-off election.

The vote at one polling station needed to be re-run on Saturday and discrepancies were noticed in results from 20 others, which are being investigated, National Elections Commission chairperson Davidetta Browne Lansanah said.

The run-off between Mr Boakai and Mr Weah was triggered after neither candidate got more than 50% of the vote in last month's first round. There were 18 other candidates.

In that vote, the president got the largest vote share and was just 7,000 votes ahead of Mr Boakai.

The poll was the tightest presidential contest in Liberia since a civil war ended about two decades ago.

Mr Boakai's campaigning focused on the need to rescue the nation from what he called "mismanagement" by Mr Weah's administration.

The president dismissed Mr Boakai's allegations, saying he had made significant strides, including introducing free tuition for university students.

This is the fourth time a presidential election has taken place since the war ended.

Observers from the regional bloc, Ecowas, deemed the run-off largely peaceful, AFP news agency reports.

But there were isolated incidents that led to "injuries and hospitalisations" in the provinces of Lofa, Nimba, Bong and Montserrado, it quotes observers as saying.