Zimbabwean police have detained another opposition lawmaker, amid a crackdown on political activity ahead of a presidential run-off election.

Eric Matinenga of the Movement of Democratic Change was arrested again Saturday after being cleared on charges of inciting violence earlier this week.

On Friday, Zimbabwean authorities forced presidential challenger Morgan Tsvangirai to stop campaigning and detained him for second time in a matter of days.

The MDC says supporters of President Robert Mugabe are trying to intimidate the party ahead of the June 27 presidential runoff.

They say more than 60 of its supporters have been killed and hundreds more injured in government-sanctioned violence.

Party officials say security forces have told them not to hold any more rallies, though it was not clear if the order signaled a nationwide ban on the MDC campaigning.

There was no immediate comment from Zimbabwean authorities.

On Thursday, police and government supporters stopped British and U.S. diplomatic staff north of Harare and forced them to go to the local police station.  They were later released.

The United States condemned the incident as "absolutely outrageous," while in London, Britain summoned Zimbabwe's ambassador for an explanation.

Both Britain and the United States have been harsh critics of the Mugabe government's actions before and since Zimbabwe's general elections in March.

Mr. Tsvangirai defeated Mr. Mugabe in that vote, but official results showed him falling short of the majority needed to avoid a runoff.

President Mugabe has ruled Zimbabwe since the country gained independence from Britain in 1980.

Some information for this report was provided by AFP, AP and Reuters.