Southern African leaders meeting in Tanzania have appointed South African President Thabo Mbeki to mediate dialogue between opposition political parties and the government of Zimbabwe.

The leaders from the 14-nation Southern African Development Community issued a statement Thursday that also called for the lifting of Western sanctions against Zimbabwe's government. African leaders concluded their emergency meeting one day after Zimbabwe police raided the main opposition Movement for Democratic Change party headquarters in the capital, Harare.

MDC officials say opposition leader Morgan Tsvangirai was briefly detained and released Wednesday, although police deny he was in custody. The opposition says at least 60 people were detained, including reporters who had gathered for a scheduled news conference.

MDC Secretary-General Tendai Biti Thursday denied police reports that explosives had been seized in the raid. He said police ransacked the headquarters, taking only party computers and documents.

Zimbabwe police say Wednesday's raid on opposition headquarters was part of a probe into a recent string of fire bombings.

The U.S.-based group, Human Rights Watch, has accused Zimbabwe's security forces of arresting and beating opposition supporters and ordinary citizens in an effort to crush all dissent.

Two weeks ago, Zimbabwe police broke up an anti-government rally and beat key activists, including Tsvangirai.

Zimbabwe has suffered several years of economic decline, culminating in chronic shortages of food and fuel, and soaring rates of inflation and unemployment.

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