Uganda police Friday raided the headquarters of opposition party Forum for Democratic Change in Kampala, and arrested its presidential candidate Kizza Besigye, FDC president Mugisha Muntu, chairman Wasswa Biriggwa and an activist Ingrid Turinawe.

It is not yet unknown where the FDC top leaders were taken by the police, who have also sealed off Entebbe Road where the party's head office is located.

Earlier there was heavy police deployment with a helicopter circling above the FDC offices.

The police fired teargas at supporters at the scene where the party was expected to hold a news conference. The police are said to have demanded the FDC officials to call off the planned press briefing which resulted in a standoff after the party leaders declined.

Preliminary election results put incumbent Yoweri Museveni on the lead with 62 per cent followed by Besigye at 33.5 per cent after votes were counted at 37 per cent of polling stations.