Bangladesh opposition protesters are set for a mass march across Dhaka, the country's capital, in a bid to derail the controversial January 5 elections, despite a police ban on the demonstration.

The opposition, which is boycotting the polls, predict that up to a million people will descend on the capital on Sunday in an effort to pressurise Prime Minister Sheikh Hasina to halt what it has described as a "farcical" election.

Police have banned the so-called "March for Democracy" amid fears that the rally would become a focal point for more unrest after what has already been the deadliest year of political violence in the country's history.

Police have detained more than 750 opposition supporters as a "preventive measure", while authorities have suspended Dhaka-bound bus, ferry and train services, virtually cutting off the city from the rest of the country.

It seems the government has imposed an undeclared shutdown in the country

Fakhrul Islam Alamgir, opposition leader

"It seems the government has imposed an undeclared shutdown in the country," Fakhrul Islam Alamgir, a leading opposition figure, said late on Saturday.

Alamgir urged supporters to defy the ban and march to central Dhaka where Khaleda Zia, leader of the opposition Bangladesh Nationalist Party (BNP), was expected to address a mass rally on Sunday afternoon.

It was unclear whether Zia would herself make it to the rally, with supporters accusing authorities of keeping her under de facto house arrest since Wednesday.

Police and security forces have conducted nationwide raids, searching trains and buses to arrest opposition supporters.

They have also set up check posts for passengers and commuters at the entry points to Dhaka.

Security has been tight in the city with around 11,000 officers and the elite Rapid Action Battalion patrolling the streets and key flashpoints.

The opposition headquarters at Nayapaltan neighbourhood in central Dhaka has been sealed by a barbed wire barricade manned by police and elite forces. 

Source: Agencies