Police in Bangladesh said Sunday that they have arrested more than 5,000 criminal suspects in the past few days as part of a broad crackdown to try and stop a growing wave of brutal attacks on minorities and liberal activists.

Since the crackdown began on Thursday, police have arrested 5,324 people, including 85 suspected Islamist radicals, said police spokesman Kamrul Ahsan. The majority of those arrested have petty criminal records. More arrests are expected through this week.

All arrests were made on specific charges, national police chief A.K.M. Shahidul Hoque said, relating to firearms, narcotics and other offences.

“We will have to prevent the emergence of militancy collectively as a whole nation,” Hoque said.

At least 18 people, including atheist bloggers, foreign aid workers and religious minorities, have been killed in attacks over the last two years. In separate incidents last week, two Hindus were fatally attacked. The attacks have alarmed citizens in Bangladesh and the international community.

The crackdown began four days after the wife of a police superintendent who led drives against Islamist militants and drug cartels was shot and stabbed to death in the southeastern city of Chittagong. The killing caused a furor among Bangladesh’s political establishment, many of whom considered her as one of their own.

Days after that attack, Prime Minister Sheikh Hasina vowed to root out radicals and secure safety in the country.

Militants have killed more than 30 people in Bangladesh since early last year, most of them activists, foreign aid workers, members of minority Muslim sects and other religious groups.

ISIS has claimed responsibility for 21 of the attacks since its first claim in September last year and al Qaeda has claimed most of the rest, according to Site Intelligence Group, a U.S.-based monitoring service.

The government denies that either group has a presence in Bangladesh and says that home-grown radicals are responsible.

Authorities have arrested suspects in some of the 18 attacks, mostly low-level operatives accused of following orders to carry out attacks, but none has been prosecuted. Police have said they are waiting until investigations are complete before taking any suspects to court.