DHAKA: Police said they had detained the deputy head of Bangladesh's main opposition party and a string of top party officials in a major crackdown after clashes rocked the capital Dhaka on Monday.

The arrests came after police in armoured vehicles fired rubber bullets to disperse opposition demonstrators, turning the streets of central Dhaka into a battleground for nearly an hour.

Police stormed the headquarters of the Bangladesh Nationalist Party (BNP) and took into custody Fakhrul Islam Alamgir -- who as acting secretary general is second in command of the party -- and dozens of senior BNP officials and activists, driving them away in prison vans.

“We've detained him (Alamgir),” Dhaka police spokesman Masudur Rahman told AFP.

Other detained BNP leaders included its chief parliamentary whip, an ex-mayor of Dhaka and two former ministers including an ex-air force chief.

“They attacked police and created panic and anarchy,” deputy police commissioner Mehedi Hasan told reporters, adding police broke open a room at the BNP headquarters and found 10 small homemade bombs.

A spokesman for the BNP was not immediately available for comment.

Police staged the arrests after at least four small homemade bombs exploded at the BNP rally which was being held in front of the party headquarters.

The blasts triggered clashes between about 5,000 brick- and rock-throwing BNP supporters and police who responded by firing rubber bullets.

The BNP has called a nationwide strike on Tuesday to protest the police action amid continuing violence stemming from trials being held over atrocities committed during the nation's bloody war for independence from Pakistan in 1971.

Leaders of the BNP and their ally, Jamaat-e-Islami, the largest Islamic party, are being tried for war crimes by a state-appointed war crimes court.

The government accuses the opposition leaders of being part of pro-Pakistani militias blamed for much of the carnage in the war. The opposition accuses the government of staging a witch-hunt.

Three of the 12 people placed on trial have been convicted of war crimes of whom two have been sentenced to death. Since the first verdict on January 21, at least 85 people have been killed in clashes.

The government says three million people were killed in the war, but independent estimates put the death toll much lower at between 300,000 and 500,000.