More than 50 people have been killed in the past three years, many hacked to death with machetes, in murders attributed to Islamists.

Islamic State and al-Qa’ida have claimed responsibility for some of the murders, however the government has denied the existence of both groups in Bangladesh and holds local terrorist organisations responsible.

Prime Minister Sheikh Hasina has vowed to catch “each and every killer”, but opposition parties have accused the government of using the crackdown to arrest their members.

A senior police officer confirmed most of the arrests had not been of suspected terrorists but criminals who had existing ­warrants. “Only a fraction of the people who have been ­arrested are members of the Islamist militant group,” the officer said.

Author and journalist Afsan Chowdhury told The Australian the government was taking a “sledgehammer” to a problem that needed a precise and considered response.

“They were targeted killings,” he said. “They should also have been targeted arrests … some 8000 people have been arrested and yet nobody has said these are the people who killed that person, nobody has said this is the organisation that killed those two guys.

“It is obviously the work of an organisation; six or seven people come, they know exactly where to go, they kill people and then they disappear.

“They are not independent nut cases. They are a collective group of killers. So why has the government not been tracking this ­organisation? I can’t explain.”

Chowdhury said the opposition Bangladesh National Party claims that more than 2000 of its party members had been ­arrested. “The government is using the courts to ­suppress the opposition. The focus of the government is very clear … they have their eye on the 2019 elections.”

Bina D’Costa of the Australian National University said Bangladesh had a serious problem with terrorism but that the government was diverting resources to crack down on the opposition, rather than dealing with the issue.

She said Hizb ut-Tahrir had last year held a two-hour video conference talking about revolution that had been watched by more than 10,000 people.

She said while the government in Dhaka was denying the existence of ISIS and al-Qa’ida in Bangladesh, local Islamist groups were being inspired by them.

“Because the government has used so much of the strength and energy of the law enforcement agencies in controlling the opposition groups it has diverted energy and resources from actually curbing domestic terrorism or controlling these kind of militant organisations,” Dr D’Costa said.

The crackdown seems to have been sparked by the killing of Mahmuda Begum, the wife of one of Bangladesh’s most senior anti-terror police. The officer had led several operations against the Jamayetul Mujahideen Bangladesh, and its members were among those arrested in the sweep. Ms Hasina has accused the BNP and its ally, Jamaat-e-Islami, of ­orchestrating the killings to destabilise the country.

Dr D’Costa said these indiscriminate crackdowns had forced opposition groups underground.

“This is going to create a lot of problems for Bangladesh because without a viable opposition you have this one party state,” she said.

“This creates a vacuum where we have space for these kinds of militant organisations to gain legitimacy in one way or other. This is what’s happening in ­Bangladesh now.”

It could create a situation where those who were opposed to the government felt they had no choice but to join one of the radical Islamist organisations, rather than legitimate political opposition party, other analysts have claimed.