Police in Uganda say they have arrested the main opposition presidential candidate to prevent him from announcing his own election results.
Kizza Besigye was detained during a raid on his party’s headquarters in the capital, Kampala, following Thursday’s tightly contested elections.
Police also fired tear gas, as clashes broke out with his supporters.
With official results for nearly half of the polling stations declared, President Yoweri Museveni is leading.
He is running for a fifth term, after 30 years in power.
This is the third time in the space of a week that Mr Besigye has been detained.
He was released on the two previous occasions without being charged.
His latest arrest came as he was about to hold a press conference.
The US embassy in Uganda condemned the crackdown in a post on its Twitter account.
After Mr Besigye was briefly detained on Thursday, the US State Department said the arrest called into question “Uganda’s commitment to a transparent and free election process”.
It also criticised a temporary shutdown of social media, chat apps and mobile money services.
President Museveni said the decision had been taken for security reasons, and to prevent people from “telling lies”.
There is a heavy deployment of police and soldiers in neighbourhoods around the headquarters of Mr Besigye’s Forum for Democratic Change (FDC) party, reports the BBC’s Catherine Byaruhanga from Kampala.
President Museveni currently leads with 62% of the vote, while Mr Beisgye has 33%, according to provisional results released by the electoral commission.
Voting is still taking place in a handful of places where the late arrival of election materials meant that polling stations did not open on Thursday.
Commonwealth election observer mission head, Nigeria’s former President Olusegun Obasanjo, condemned the failure of voting stations to open on time.
“Delays of three, four, five and even six hours, especially in Kampala, are absolutely inexcusable and will not inspire trust and confidence in the system and the process,” he said.
A candidate needs to secure more than 50% of the vote to avoid a run-off with the second-ranked contender.
Ugandans also voted in parliamentary and local elections.
Final results are expected by Saturday