Legislators heckled each other during the first working session of the new opposition-dominated parliament Tuesday as negotiators tried to salvage Zimbabwe's power-sharing agreement, dpa reported.
Former South African president Thabo Mbeki arrives in Harare on Monday night.
Riot police also broke up a demonstration held by students outside the legislature. Witnesses saw at least three students bundled into a police van. A number of others were injured in a scuffle and had to be helped to a nearby clinic. Police comment was not immediately available.
Former South African President Thabo Mbeki, who flew to Harare late Monday, to mediate talks between President Robert Mugabe and opposition leader Morgan Tsvangirai.
Mbeki later said no conclusion was reached.
Mbeki brokered a September 15 deal between Mugabe and Tsvangirai to form a unity government.
But over the weekend, Mugabe said his party would control all key ministries, prompting Tsvangirai to threaten to quit negotiations.
The new 210-seat legislature that met Tuesday is the first controlled by the opposition since Zimbabwe gained independence in 1980. At Parliament's official opening ceremonies in August, many lawmakers jeered Mugabe.
The speech Mugabe made then was debated in a lively session Tuesday, with legislators heckling each other. Mugabe was not present.
Speakers addressed the need for the unity government to be formed so the country's humanitarian crisis can be addressed.
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But opposition legislator Sam Nkomo warned the new government should not be formed at "any cost.
"There is a need to share power equitably," he said. "We want to be genuine partners in this agreement."
Lawmakers will reconvene Wednesday, when legislation will be introduced that is necessary for the formation of the new government. The constitution needs to be changed to create the post of prime minister, which is supposed to be filled by Tsvangirai.
Mugabe's party and the opposition have been unable to agree on the allocation of Cabinet posts. The power-sharing deal calls for the opposition to control 16 Cabinet seats and Mugabe's party 15.
Mugabe's unilateral move to take control of key government ministries has been condemned by the European Union and the United States.
An official list published Saturday gave Mugabe's party portfolios for defense, home and foreign affairs, justice, mining and land, among others. The list assigned the opposition with minor ministries, such as constitutional affairs and water management.
On Tuesday U.S. State Department spokesman Sean McCormack said Mugabe had "overstepped the bounds of the agreement" by claiming key ministries.
"We would like to see is the implementation of that original agreement get back on track," he said. "And, of course, any implementation solution has to be one that is acceptable to the MDC and Mr. Tsvangirai." The MDC is the Movement for Democratic Change, Tsvangirai's party.
While politicians struggle over the shape of Zimbabwe's government, half the population -- 5.1 million people -- faces starvation, two-thirds of children are out of school, and water shortages have led to deadly cholera outbreaks in three parts of the country, according to aid agencies.