Suspected militants in Bangladesh have killed the wife of a senior police officer who is playing a leading role in investigating a spate of murders committed by Islamists, officials say, BBC reports.

Mahmuda Aktar was shot in the head in Chittagong in front of her six-year-old son.

Her husband, Supt Babul Aktar, is investigating the banned Islamist Jamayetul Mujahideen Bangladesh group.

Police say Mrs Aktar may have been killed because of her husband`s work.

Police spokesman Iqbal Bahar said that three men stabbed and then shot her.

"She came out of her apartment to put her son on the school bus [when] suddenly three people on a bike came close to her.

"First they stabbed her and later they shot her. She died immediately.

"As Babul Aktar was involved in working against the militants we will investigate whether the militants carried out this operation."