Harare  - Zimbabwe's longtime opposition leader Morgan Tsvangirai was due to be sworn in as prime minister on Wednesday to begin working with his arch-rival President Robert Mugabe on ending the country's economic and humanitarian crises.

Tsvangirai was scheduled to take the oath of office at State House in Harare around 11 am (0900 GMT) and then address a large crowd of his supporters in a football stadium.

The vice president of Tsvangirai's Movement for Democratic Change (MDC), Thokozani Kuphe, and the leader of an MDC splinter faction, Arthur Mutambara, were also to be sworn in as deputy prime ministers.

Addressing concerns about his decision to enter a unity government that is skewed in favour of Mugabe's Zanu-PF, Tsvangirai said Tuesday: "The road ahead is long but we believe we must and can succeed, while learning from our sad past, which has devastated our people."

Among the guests expected at the ceremony are former South African president Thabo Mbeki, who mediated in the formation of the government, current South African Foreign Affairs Minister Nkosazana Dlamini-Zuma and the leaders of Mozambique, Angola and Swaziland.

Wednesday's ceremony takes place under the cloud of continued state oppression against MDC members and rights activists.

Hours before Tsvangirai's inauguration, two leading human rights lawyers, one of whom has been involved in defending a group of around 30 political prisoners, were arrested. The charges against them, if there are any, were unknown.

Tsvangirai had been insisting that the prisoners, whom the state accuses mostly of conspiring to topple Mugabe, be released before he take office. By Wednesday morning, there was no sign of them being freed.

The formation of the 31-ministry government is set to continue on Friday, when the ministers are sworn in, 14 from Tsvangirai's MDC faction, 3 from Mutambara's faction and 15 from Zanu-PF. The number of ministers exceed the number of ministries by one because the MDC and Zanu-PF have agreed to "co-minister" home affairs.

After five months of bickering between the parties over positions of power, the MDC last week voted to come onboard the government to try to alleviate the suffering of Zimbabweans. Thousands of Zimbabweans have died of cholera in recent months, mostly for lack of clean water, and around 7 million cannot adequately feed themselves. (dpr)