Zimbabwean opposition leader Morgan Tsvangirai was held by police for the third time in a week while campaigning for the June 27 presidential run-off election.

His Movement for Democratic Change said in a statement that he was arrested in the town of Kwekwe on Thursday while on a tour of Zimbabwe's Midlands province.

"The [party] president's convoy, which includes a personalised campaign bus, was ordered to drive to Kwekwe Police Station," the party said. "The convoy had initially been stopped a roadblock just before Kwekwe... No charge has yet been preferred."

The news came hours after MDC Secretary-General Tendai Biti was arrested at Harare International Airport upon his return from South Africa. The party said Biti's whereabouts were unknown. "He was last seen being shoved, with hands handcuffed, into a Mercedes Benz, registration number AAO 3822," the party said.

The MDC alleged in its statement that earlier on Thursday, after Tsvangirai had visited an MDC member of parliament at his home, activists of the ruling Zanu PF party had stoned the house and looted property. And in the next town, Kadoma, other Zanu PF supporters beat up onlookers who had waved at Tsvangirai's campaign bus.