MP Mohibur Rahman Manik, of the governing Awami League, was out of town, but the blast at his home in the northern district of Sylhet left two of his relatives dead.

"The bomb was apparently thrown from outside a window but it could not be confirmed until an investigation was complete," said the Deputy Inspector-General of Police, Tofazal Hossain.

It is the latest incident in a wave of violence since February, believed to be politically motivated.

Reporting from Dhaka, the BBC's David Chazan says Bangladeshis are shocked by the rise in political violence.

Fundamentalists blamed

Earlier this month, 10 people were killed in a bomb attack on a cultural festival.

The authorities blamed that bombing on Islamic fundamentalists who appear to be extending their activities in Bangladesh.

And last month, gunmen opened fire at a political rally, killing six leaders of a small party in the coalition government. Police blamed an ultra-leftist group.

Newly-appointed Interior Minister Mohammad Nasim has promised to make arrests in the bombing cases his first priority.

Donors concerned

Bangladesh's aid donors are worried about the government's failure to engage in political dialogue with the opposition and the opposition's readiness to call strikes and take to the streets.