DHAKA (AFP) - Bangladesh security forces arrested more than 100 protesters on Thursday as they launched a nationwide crackdown on the opposition ahead of the controversial Jan 5 general election.

Officials said the protesters were detained in joint operations by the police, the elite Rapid Action Battalion (RAB) and paramilitary border guards amid a series of transport blockades called by opposition parties which are boycotting the polls.

The "joint forces" arrested 118 people, mostly activists from the main opposition Bangladesh Nationalist Party (BNP) and its key ally Jamaat-e-Islami, in five districts where police had earlier clashed with demonstrators.

The BNP, Jamaat and their smaller allies have been staging protests since late October to try to force Prime Minister Sheikh Hasina to step down so that a neutral caretaker government can oversee the election.

She refuses to accept the arrangement, which was in place during previous national polls.

The BNP has refused to field candidates for the January election, saying the vote under Ms Hasina will be rigged - an accusation the premier flatly rejects.

Jamaat, the country's largest Islamist party which has been barred from contesting the polls, is also furious with the government after one of its leaders was executed last week for crimes during the 1971 independence war.

Protests over the divisive polls and the war crime trials have left at least 264 people dead since January, making this year the bloodiest in Bangladesh's history.

Of the 118, 37 protesters were arrested in Rajnagar village in the western district of Meherepur, local police chief Nahidul Alam said.

"Most of them are Jamaat activists," he said.

"They are anarchists. They cut trees to put blockades on the roads, threw crude bombs and attacked lorries. They're arrested in a joint operation by police, RAB and BGB (Border Guard Bangladesh)," Alam told AFP He said the detainees were also accused of twice in the past week cutting an optical fibre line that severed telecommunications links to a western district and also hit calls to neighbouring India.

Police said another 38 Jamaat activists were arrested in the troubled Satkhira district in a series of pre-dawn raids on remote villages.

The opposition, which has enforced a 72-hour nationwide blockade since Tuesday, has announced a new four-day blockade across the country from Saturday in their bid to topple Ms Hasina and foil the January polls.