Police have detained hundreds of opposition supporters in Bangladesh, authorities have said, in an effort to stop protesters reaching the country's capital a day before a mass anti-government march.

The move came after opposition leader Khaleda Zia vowed on Friday to go ahead with a demonstration planned for Sunday despite a police ban on protests ahead of January 5 elections.

Al Jazeera's Tanvir Chowdhury reported from Bangladesh on Saturday that the country's security forces had rounded up passengers on buses, trains and ferries, and that many of them told local television stations that they had no connection to the scheduled opposition rally. 

Police officers told the AFP news agency that more than 750 people have been arrested after raids on houses and trains over the past two days in a nationwide crackdown on opposition supporters.

Police made the arrests "to prevent acts of violence and sabotages" ahead of the opposition rallies, Dhaka police spokesman Masudur Rahman told AFP.

Local media reported that the detainees were harassed and intimidated by the police, Chowdhury said. 

Dhaka-bound public transports have been halted as operators suspended their services following orders from the government.

'Prevent violence'

The opposition, which is boycotting the elections, has said that up to a million people would descend on the capital in Sunday's protest aimed at forcing Prime Minister Sheikh Hasina to call off the polls.

Police said they could not give approval for what Zia has called a "March for Democracy" amid fears the protest would become a focal point for more unrest after months of deadly political violence.

There was doubt whether Zia would be able to take part in the protest herself with supporters accusing authorities of keeping her under de facto house arrest since Wednesday.

Although authorities deny that Zia is under house arrest, they concede that police reinforcements have been posted outside her home in an upmarket district of Dhaka to "enhance security".

Chowdhury reported that Zia's house has been cordoned by security forces and no one was allowed to visit her. 

Source: Al Jazeera and agencies