Bangladesh's main opposition party said Thursday police had arrested hundreds of supporters in a sweeping crackdown a day ahead of anti-government protests planned in the capital Dhaka.

"Police have arrested at least 538 of our people since Wednesday," Zahir Uddin Swapan, the spokesman of the Bangladesh Nationalist Party (BNP), told AFP, alleging a former councillor had also been beaten.

Faruq Ahmed, Dhaka Metropolitan Police spokesman, said officers had detained 366 people since Wednesday but made no comment on their political background.

Dhaka police deputy commissioner Hayatul Islam Khan said some BNP supporters were detained in a hotel in the capital but gave no further details.

Local daily Prothom Alo, quoting police sources, said 411 people had been detained, including 366 BNP supporters.

The BNP and dozens of smaller allies have called for protests throughout Bangladesh demanding Prime Minister Sheikh Hasina step down and that polls slated for January take place under a neutral caretaker government.

Hasina has rejected the demand, saying it is unconstitutional.

Hasina's Awami League has ruled the world's eighth most populous country since 2009 and has been accused of human rights abuses and corruption.

Police refused permission for a protest on Thursday but said rallies on Friday could go ahead, a weekend in Muslim-majority Bangladesh.

Protests earlier this month drew tens of thousands of people. One opposition activist died and hundreds were injured in clashes on July 18, with the opposition blaming ruling party supporters.

Western governments have expressed concern over the political climate in Bangladesh, where Hasina's party dominates the legislature.

Her security forces are accused of detaining tens of thousands of opposition activists, killing hundreds in extrajudicial encounters and disappearing hundreds of leaders and supporters.