DHAKA (AFP) - Bangladesh police fired rubber bullets and tear gas at opposition protesters Sunday before the start of another three-day strike intended to force Prime Minister Sheikh Hasina to quit.

Protesters exploded home-made bombs and clashed with police during small rallies in and near Dhaka as part of the opposition's campaign to force Hasina to install a neutral caretaker government for upcoming elections.

The main opposition Bangladesh Nationalist Party (BNP) and its Islamist allies have called a nationwide strike starting Monday as part of the campaign that started last month and has left some 20 people dead.

Police Inspector Abul Kalam Azad said officers fired rubber bullets and tear gas at about 2,000 protesters after they attacked cars and tried to torch buses at Tongi, just outside the capital.

"The protesters also exploded two small crude bombs. We've arrested at least 15 of them on charges of violence," he told AFP.

Fire official Mohammad Ali told AFP at least six buses and two cars were set ablaze in Dhaka.

A young man was critically injured after a bomb that he was carrying exploded in central Dhaka.

"Part of his thigh was blown away in the explosion. He has been operated on at a Dhaka hospital," said local police chief Sirajul Islam.

Monday's strike is the latest called by the BNP as part of its campaign that started on Oct 25, and has seen violent street clashes between opposition and ruling party activists and with the police.

At a large rally in the capital on Sunday, Ms Hasina repeated her offer of further talks with the opposition to try to defuse the crisis, but said the BNP must first call off the strike.

The BNP has branded the current government "illegal" and says that under the law a neutral caretaker government must be set up three months before national elections, due in January.

Ms Hasina has scrapped the caretaker system and instead proposed an all-party interim government led by herself to oversee the polls.