Dhaka: Authorities in Bangladesh arrested nearly 150 suspected militants and more than 11,000 others as part of a crackdown on extremism after a wave of brutal killings, Bengali officials say on Wednesday.

Police said they detained 145 suspected Islamist militants over four days of raids and that the rest were accused of everything from theft and drug dealing to violence.

An officially secular but Muslim-majority nation, Bangladesh has seen a surge of targeted killings -- blamed on Islamist radicals -- that have claimed the lives of secularists, religious minorities and gay activists.

Police have said that most of the suspected militants were members of Jama'atul Mujahedin Bangladesh, a banned Islamist group.

But the opposition Bangladesh Nationalist Party, or BNP, said the raids were designed to detain its leaders and workers. It said some 2,100 party leaders and activists were arrested.

The JMB also has been blamed for bomb attacks, and members of the group were detained in relation to the recent killing of a Hindu priest.

Last week, the wife of a senior police officer who had led high-profile operations against the group was stabbed and shot to death while taking her to son to catch his school bus.

Police seized arms, ammunition, other lethal weapons and more than 2,000 motorbikes during this week's raids.

Marcia Bernicat, U.S. ambassador to Bangladesh, said there have been at least 35 such attacks carried out over 14 months, with an Islamist terror group claiming responsibility for 23.