Parliament had been expected to hear a no-confidence motion against the speaker, Abdulla Masheeh, but MPs found their way blocked, the Maldivian Democratic Party said.
Party spokesperson Hamid Abdul Ghafoor added several opposition MPs broke through the military cordon only to be pepper sprayed and evicted.
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"On Monday morning the gates of the parliament were padlocked by members of the armed forces and MPs were forcibly prevented from entering the parliamentary compound," the opposition party said in a statement.
There was no immediate comment from the government.
The opposition this month secured enough support from government defectors to begin impeachment proceedings against the speaker, in a bid to wrest control of parliament from Yameen before presidential elections next year.
The government has repeatedly tried to frustrate these efforts. It arrested several opposition MPs last week ahead of the vote, and scuttled a past no-confidence bid by raising the number of signatures required for a successful motion. The first attempt to impeach the speaker in March sparked chaos when Yameen ordered troops to enter parliament and remove dissenting opponents by force.
The political turbulence has seen the international community, including the United States, urging the Maldives to safeguard democracy.
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The opposition coalition, led by exiled former Maldives president Mohamed Nasheed, wants to defeat Yameen at elections next year but faces an uphill battle. All their key leaders are imprisoned or have fled to avoid a lengthy crackdown on dissent under Yameen's leadership.
The instability has threatened to dent the Maldives' image as a tourist paradise.
Nasheed became the Maldives first democratically-elected president in 2008, but was narrowly defeated by Yameen in a controversial 2013 election run-off.
In 2015, he was sentenced to 13 years in prison on terrorism charges that were widely seen as politically motivated. He now lives in exile in Britain.
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