The blasts occurred after midnight in a crowd of several thousand attending the festival, organised by the Udichi Shilpi Goshti group, the cultural wing of the Communist Party of Bangladesh.

Doctors work on one of the wounded

Five people were killed on the spot, others died later. Among the dead were two Udichi members.

Ambulances ferried the injured to local hospitals as the concert-goers fled in panic. Hospitals are now struggling to treat an estimated 75 injured people.

A police spokesman said they suspected Islamic militants were behind the attack, but no group has so far claimed responsibility.

Udichi, which staged a protest march in Dhaka on Sunday, did not blame anyone directly, but described the bombing as an "organised attempt" to kill its leaders.

Prime Minister Sheikh Hassina has condemned what she called a barbaric act.

News of the explosions has shocked the country. Bangladeshis are used to political and gang violence, particularly in the south, where more than 1,000 were killed in clashes between rival leftist groups last year.

According to the BBC's Dhaka Correspondent, David Chazan, the apparently indiscriminate nature of the explosion has terrified people in the area.

Recent violence

The blasts follow complaints by some Bangladeshis of an upsurge of lawlessness in some parts of the country and fears of a rise in Islamic militant activity.

Two weeks ago the killings of five politicians at a rally in western Bangladesh prompted calls for a campaign to root out banned political groups and outlaw gangs.

In January, a leading poet was attacked by Islamic militants who said they were linked with Osama bin Laden - the man suspected of masterminding an attack against the American embassy in Kenya last year.

There have been unconfirmed reports that Mr bin Laden has been funding some Islamic groups in Bangladesh whose members are thought to be mainly Bangladeshis who fought in Afghanistan.