POLICE in Uganda have arrested opposition leader Kizza Besigye at his party's headquarters after heavily armed officers surrounded the building and a helicopter fired tear gas at a crowd.
Vote counting continued in the country's tumultuous elections as Mr Besigye challenges President Yoweri Museveni at the ballot box.
Semujju Nganda, a spokesman for Mr Besigye's Forum for Democratic Change party, said police took him to an unknown location, and later fired tear gas and live ammunition into the air as warning shots, as well as detonating stun grenades.
Mr Besigye had been holding a meeting with other leaders of his party in Kampala, aide Ingrid Turinawe said.
"The police basically invaded us," she said.
Armed police also parked their trucks near the gate of the home of another presidential candidate, former prime minister Amama Mbabazi.
Josephine Mayanja-Nkangi, a spokeswoman for Mr Mbabazi, said he understood the deployment means he cannot leave his house.
Protesters erected barricades of stones on the road leading to Uganda's only international airport. Police fired tear gas and struck demonstrators with sticks.
Voting on Thursday suffered delays in delivery of voting materials, especially in areas seen as opposition strongholds. Voting is still taking place at 36 polling stations in Kampala and the neighbouring district of Wakiso.
The government also shut down sites such as Twitter and Facebook, but using virtual private networks, many Ugandans are slowly getting back on social media.
Mr Besigye was also briefly arrested late on Thursday after visiting a house in Kampala where he suspected ballot-stuffing was taking place. Police said the house was a security facility and accused him of trespassing on government property.
Mr Besigye's party is running its own tally centre and claimed some results being announced by the election commission are a "concoction", Ms Turinawe said, noting that the election commission is announcing results according to tallies from polling stations, not according to districts as had been expected.
Provisional results released on Friday showed Uganda's long-time president with an early lead over Mr Besigye. Final results are expected on Saturday. More than 15 million people were registered to vote, with members of parliament also up for election.
Mr Museveni (71) took power in 1986 and pulled Uganda out of years of chaos. He is a key US ally on security matters, especially in Somalia. His critics worry he may want to rule for life, and accuse him of using security forces to intimidate and harass the opposition.
Mr Besigye (59) was Mr Museveni's personal physician during a bush war and served as deputy interior minister in his first cabinet. He broke with the president in 1999, saying he was no longer a democrat.
