Dhaka - At least 15 people, including policemen and journalists, were injured Friday when detained militants from an outlawed Islamist group exploded a grenade after a press conference in a police station in Bangladesh, police said.

A member of the banned Islamist outfit, Jamaatul Mujahideen Bangladesh (JMB), exploded the grenade inside the conference room of the police building in Gazipur, 37 kilometres north of Dhaka, immediately after the police chief, Abdul Baten, briefed local reporters on an anti-militants drive.

Earlier, the security forces had captured the four alleged militants, three of them female, from a house in Gazupur and recovered five grenades. They also seized huge quantity explosives and of bomb-making materials.

The district police chief, Baten, who escaped the attack unhurt, said one of the suspected militants handcuffed in custody suddenly grabbed one of the seized grenades and exploded it soon after the press conference ended.

He said the attack left seven people severely injured.

The attack came a day before Bangladesh celebrates International Mother's Language Day, commemorating the establishment of Bengali as state language.

The JMB, which calls for Sharia law in Bangladesh, is responsible for a number of recent attacks on public places killing dozens of people.

The outfit is also responsible for the synchronised bomb attacks at 61 regional headquarters in 2005.

Six senior six leaders of the group were condemned to death and hanged in early 2007. (dpa)