DHAKA (Reuters) - Bangladesh has arrested four members of an outlawed militant group, including the chief of its women's wing, police said on Sunday, as authorities intensify a crackdown on militants.

The arrest follows Indian security officials' exposure of a plot last month targeting Prime Minister Sheikh Hasina. Two members of a banned Bangladesh group were killed in an explosion while building bombs in India's eastern state of West Bengal, just over the border with Bangladesh.

Police said they arrested Fatema, the chief of the women's wing of Jamaat-ul-Mujahideen, whose husband Sajid was arrested by Indian police in connection with the West Bengal blast.

"Fatema and three men were arrested in a raid in Dhaka and we also recovered a huge quantity of bomb-making materials and explosives," police spokesman Monirul Islam told a news conference.

The group also planned to assassinate the country's main opposition leader, Khaleda Zia, Indian officials said. Hasina and Zia have dominated Bangladeshi politics for more than a decade.

Last week, a team headed by the chief of India's main counter-terrorism arm, the National Investigations Agency, held talks with Bangladeshi officials in Dhaka and handed over a list of 11 suspects thought to be hiding there.

Under Sheikh Hasina, Bangladesh has been working closely with India to tackle militant groups, including the handover of those India suspects of stirring up trouble in its remote northeast.

The Jamaat-ul-Mujahideen was thought to have been lying low since a crackdown by authorities after it detonated nearly 500 bombs almost simultaneously on a single day in 2005 across Bangladesh, including in Dhaka, the capital.

In subsequent suicide attacks on several courthouses, its militants killed 25 people and wounded hundreds.

A security van taking members of the group to court earlier this year was targeted by gunmen who opened fire and tossed bombs at the vehicle.