HARARE, Zimbabwe -- Zimbabwe's main opposition party won the top job in parliament Monday, scoring a surprise victory that could give President Robert Mugabe's foes leverage in power-sharing talks.

The election of Lovemore Moyo of the Movement for Democratic Change on a 110-98 vote brought cheers, with opposition legislators breaking into a song declaring "ZANU-PF is finished!" The result indicated some members of the ruling ZANU-PF may have voted for Moyo in the secret ballot.

Mugabe's party had held a parliamentary majority since independence, but it emerged from March elections with 99 seats in the 210-seat legislature, just behind the 100 held by the Movement for Democratic Change. A splinter opposition party has 10 seats and an independent one.

ZANU-PF had been expected to retain the speakership in a body that long had been a rubber-stamp for Mugabe's policies, but it surprised many people by not putting up a candidate.

"The figures were against us," said ruling party legislator Walter Mzemdi. He said ZANU-PF lawmakers were instructed to vote for Paul Themba-Nyathi, a leader of the splinter opposition faction, but the total for Moyo showed some backed him.

Moyo promised to "work toward a professional parliament that will represent the true wishes of the people of Zimbabwe."

If the opposition continues to win support from the splinter faction, it would have the simple majority needed to cripple Mugabe by blocking funds for government ministries and projects.

Without that support, however, the assembly could mire in deadlock. That could be a boost to Mugabe, who retains power to dissolve parliament and rule through emergency regulations imposed by presidential decree.

Political observers agree the opposition cannot summon the two-thirds vote needed to impeach Mugabe, forcing the two sides to continue efforts to figure out a way to work together.

Simandla Zondi, an analyst at South Africa's Institute for Global Dialogue, said Moyo's victory marks "the beginning of power-sharing not by consensus but by issue of the electoral weight" of the opposition party.

"It gives them a significant amount of power to build the legislative assembly into a strong force for accountability, one which is really going to force the executive (Mugabe) to find a way to work with a parliament which may be led by hostile forces," Zondi said.

He said the legislative vote also could be an opposition bargaining chip in stalled power-sharing negotiations aimed at resolving the political crisis produced by Zimbabwe's disputed presidential election.

In the March 29 voting, the Movement for Democratic Change led by Morgan Tsvangirai defeated Mugabe's party for the first time in legislative races, but the official results in the presidential ballot gave no candidate the simple majority needed for victory.

Mugabe was once immensely popular, but he has seen his standing eroded by heavy-handed treatment of opponents and by the sometimes violent seizure of white-owned commercial farms that wrecked Zimbabwe's agriculture sector -- the base of what had been one of Africa's rare economic success stories.

Tsvangirai, who led the initial round and claimed he was denied a victory by vote fraud, was scheduled to face Mugabe in a June run-off. But the opposition leader dropped out of the race after weeks of violence aimed at his supporters. Mugabe held a one-man runoff that was widely condemned at home and abroad.

Tensions remain high between the two sides.

Mugabe's decision to officially open parliament Tuesday breaks an agreement he signed last month with Tsvangirai that the assembly would not sit unless both men agreed or until a power-sharing deal was struck.

Tsvangirai's party also charged last week that Mugabe's party was trying to buy its legislators off in the contest for speaker.

On Monday, shortly before the election for speaker, two opposition legislators were arrested. Lawmaker Sure Mudiwa was held only briefly and later was among the 208 parliament members sworn in. But the second, Elia Jembere, did not reappear.

Jembere is among seven opposition activists charged by police with involvement in election violence. Independent human rights groups say Mugabe's supporters are responsible for most violence.

An opposition statement said police also tried to arrest a third member of parliament who is a negotiator at the power-sharing talks, but he "was rescued" by fellow legislators.

Police spokesman Wayne Bvudzijena said he was unaware of Monday's arrests. "It would be illegal for anyone to be arrested while they were proceeding to parliament," he said.

Opposition spokesman Nelson Chamisa said the arrests were an attempt by Mugabe's party to regain control of parliament.

"ZANU-PF are in a desperate attempt to try and stop or abort our victory," Chamisa said. "It's a struggle. We have to fight it out."

The arrests and a government announcement Monday that Mugabe had appointed loyalists to several posts as senators and governors were likely to fuel opposition charges that Mugabe is undermining the power-sharing talks.

Leaked documents say Tsvangirai balked at signing a deal that would make him prime minister with limited powers and answerable to Mugabe, who would remain president with virtually all his powers intact.