Kuala Lumpur - Malaysian police on Thursday detained dozens of demonstrators, including opposition lawmakers and politicians, in a large street protest outside the northern Perak state assembly.

Riot police, part of a large police presence, barricaded the entrance to the state parliament, allowing only those with official documents to pass through.

Dozens of protestors have so far been detained, including four lawmakers from the opposition Democratic Action Party, party leader Lim Kit Siang said.

Police have yet to confirm the number of people placed under remand.

Perak has been the venue of an increasingly complicated and fierce tussle for power between the opposition and the ruling National Front government which orchestrated a power take-over in February.

The government's move to wrest control of the state from the opposition People's Alliance, which won Perak in last year's general elections via lawmaker defections, sparked criticism and claims that the takeover was unconstitutional.

Police had earlier warned against any demonstrations on Thursday, when the assembly is reconvening for the first time since the takeover.

Chaos and pandemonium also reigned inside the legislature, as government and opposition lawmakers traded barbs and argued over who had the right to sit in the assembly, the Star online news portal said.

The opposition has been calling for fresh state elections to resolve the stalemate, a demand resisted by the government.

The Perak crisis is a dark stain on newly appointed Prime Minister Najib Razak's administration, despite his pledges for a more open media and voices of dissent to be heard.

The detention of an anti-government activist and one opposition lawmaker Wednesday for making allegedly seditious remarks have raised fears that Najib is intent on cracking down on opposition.

"Malaysians and the world today witness another unethical, undemocratic, illegal and unconstitutional power grab," Lim said in his blog. (dpa)