Unidentified attackers threw the bomb at offices of the Awami League in the south-western city of Khulna, killing local party leader Kamrul Islam.

No-one has claimed responsibility for the attack, which follows the killing in the city two days ago of another Awami League official.

"We still have no clue to who were the culprits," one police officer told Reuters news agency.

Local reporters said six of the wounded were in a critical condition.

The situation has been tense in Khulna since a number of killings last month, for which left-wing militants admitted responsibility.

The opposition party has accused the governing Bangladeshi Nationalist Party of being behind the recent spate of killings.

The governing party has rejected the allegation.