Police have lined the road near the headquarters of Zimbabwe's opposition MDC Alliance headquarters in the capital, Harare, a BBC correspondent has shown in a tweet.

He describes it as a "stand-off" adding that the police want to go in and make arrests.

On Wednesday, MDC Alliance supporters clashed with security forces on the streets of Harare leaving three people dead.

The opposition says its candidate, Nelson Chamisa, won Monday's presidential election, pre-empting an official announcement. It has alleged the result is now being rigged.

The electoral commission has urged people to remain patient, adding that no cheating is going on.

It has to announce the result by Saturday.