HARARE, Zimbabwe - Zimbabwe's main opposition group declared itself the country's new ruling party yesterday and convened what it called a session of parliament, in defiance of President Robert Mugabe.

In a self-proclaimed "state of the nation" address, Movement for Democratic Change leader Morgan Tsvangirai said Zimbabwe was about to witness "a new and different era of governance."

Tsvangirai asked his party's newly elected lawmakers, gathered at the Harare International Conference Center, to stand for a minute's silence for the more than 50 people who have died in political violence since the March elections. Tens of thousands of opposition supporters have been driven from their homes.

He described Mugabe's ZANU-PF party as now in opposition.

The former opposition group won 110 seats in the 210-seat parliament in March elections, which gave it control of the legislature for the first time since independence from Britain in 1980. Mugabe's party won 97, and three by-elections are pending. Parliament has not yet met.

Tsvangirai also won the presidential ballot but not by an outright majority, according to official results. He faces Mugabe in a runoff June 27.

"I can't see Tsvangirai winning," Zimbabwe Justice Minister Patrick Chinamasa told reporters in the South African capital, Pretoria. "If he wins, it will be a destabilizing event in Zimbabwe."

He said the ruling party had learned from mistakes in the first round, would mobilize more voters for the runoff, and was confident of victory.

"We went into the election divided within ourselves," Chinamasa said. "We have now reconciled and closed ranks behind our candidate."

Many observers fear that the 84-year-old Mugabe will use intimidation and violence to steal the election.

Tsvangirai's "parliament session" was expected to anger Mugabe's party.

"Healthy democracies have at least two parties, and a reformed ZANU-PF should be one of them," Tsvangirai said.

Tsvangirai said the Movement for Democratic Change should woo "those peaceful members of ZANU-PF whose eyes are open to the disastrous state of our nation."

He said party lawmakers should immediately begin work on a timetable to rewrite the constitution and repeal sweeping security and media laws, along with changes needed to restore the economy.

"We are an unmitigated embarrassment to the African continent," Tsvangirai said. "Very soon will be the time for celebration, but now is the time to get down to work."

The party proposed establishing a Truth and Justice Commission that would investigate crimes against ordinary people and work out compensation for victims.

Tsvangirai said there would be no witch-hunt against police, soldiers or civil servants.

"But there will be no tolerance or amnesty for those who continue to rape and kill our people," he said.