Zimbabwean President Robert Mugabe was loudly heckled by members of the biggest party, the Movement for Democratic Change (MDC), as he opened parliament in Harare in a controversial move.

Mugabe struggled to be heard above the din from the ruling party benches, which Morgan Tsvangirai's MDC occupied for the first time in its history this week. The party took more votes than Mugabe's Zanu- PF in March elections but too few for a parliamentary majority.

The MDC had initially threatened to boycott the opening, saying it did not recognize Mugabe as president after his victory in a June run-off vote that Tsvangirai refused to contest because of a spate of political violence directed at his supporters.

But the party reviewed its stance after its candidate, Lovemore Moyo, on Monday defeated the Zanu-PF candidate in the vote for speaker of parliament - the fourth-most important position in Zimbabwean politics.

Moyo was in parliament to receive Mugabe when he arrived for a tumultuous ceremony, marked by open derision towards the elderly leader from MDC deputies.

Referring to his reelection, Mugabe said his win had been preceded by "cases of regrettable and isolated political violence." This was met with a chorus of boos from the MDC, which says more than 125 of its members have been killed by Mugabe supporters since March.

On his talks with Tsvangirai on a power-sharing government, Mugabe said there was an "expectation that everyone will sign up," prompting another round of hissing and whistling from the MDC.

Mugabe has repeatedly cast Tsvangirai as the spoiler for failing to agree to his terms for power-sharing, which would see him retain significant executive powers and leave Tsvangirai a relatively toothless prime minister.

Tsvangirai is demanding full control of the government, as he took the most votes in the last credible presidential elections in March.

Flogging a by now familiar hobby horse, Mugabe lashed out at what he called a "foreign hand" in Zimbabwe's economic demise.

The "destructive hand of our enemies" was evident both in rising food prices and the destabilization of Zimbabwe's currency, he said.

Zimbabwe is in the throes of a grave economic crisis that has forced Mugabe into talks with the donor-backed MDC.

After Tsvangirai refused to sign up to the deal on the table, Mugabe got the go-ahead from his neighbours in the Southern African Development Community (SADC) to convene parliament.

He was expected to follow that up by appointing a cabinet, possibly with some support from a breakaway MDC faction led by Arthur Mutambara.

But Monday's vote for speaker looks to have stymied those plans. Tsvangirai's MDC won the position, after apparently siphoning some support in the secret ballot from within Mugabe's own party and Mutambara's faction and despite the arrest of two of its MPs.

The two were later released and returned to vote.

On Tuesday, the police crackdown on the MDC continued with the arrest of Elton Mangoma, a negotiator for the party who has been involved in the negotiations with Zanu-PF.

Mangoma's arrest at his home comes a day after MDC MPs blocked a first attempt by police to detain him along with the two other MPs at parliament.

A police official said merely: "Police have been looking for him for some time now. We want him to assist us."

Analysts see the MDC win as likely to strengthen Tsvangirai's hand when the negotiations with SADC resume under the mediation of South African President Thabo Mbeki.

Zimbabweans are counting on a negotiated settlement to end nearly a decade of worsening hardship and political repression under Mugabe, who has ruled Zimbabwe since 1980.