At least four persons were killed in fresh clashes in Bangladesh on Sunday, taking the death toll to 25 in violence triggered by the execution of a senior Jamaat leader, even as Prime Minister Sheikh Hasina warned of a crackdown on rioters.

Helicopters patrolled the skies over Dhaka while paramilitary troops guarded major cities as the violence continued unabated over Jamaat-e-Islami leader Abdul Quader Mollah’s execution for 1971 war crimes three days ago.

Elite anti-crime Rapid Action Battalion (RAB) officials said they decided to use helicopters over Dhaka and wherever it was required and “the aerial patrol will continue as long as the situation demands” as Jamaat on Sunday enforced a nationwide strike protesting Mollah’s execution.

Jamaat workers stabbed to death an Awami League supporter on Sunday, hours after three Islamists were killed in a clash with police in northern Lalmonirhat district.

Ten people belonging to minority Hindu community were injured when Jamaat activists attacked and set afire their houses at Kafirbazar area in the district, reports said.

At least 25 people have been killed in clashes since Thursday night, when Jamaat leader Abdul Quader Mollah, known as the “Butcher of Mirpur” was hanged for atrocities committed during Bangladesh’s 1971 liberation war against Pakistan.

Mollah, who was hanged after the Supreme Court rejected his review petition, became the first politician to be put to death for war crimes.

Violence erupted at several places soon after his execution, which the Jamaat described as a “political murder” even as it vowed to take revenge.

Addressing a rally marking the 42nd anniversary of Martyred Intellectuals Day on Saturday, Ms. Hasina accused her arch-rival and main opposition BNP chief Khaleda Zia of backing Jamaat to protect the perpetrators of crimes against humanity.

“We have shown enough patience. We will not tolerate anymore. People of the country know how to reply these atrocities, we (government) also know how to respond to, control you,” she said.

Her comments came as Jamaat called a nationwide strike today to protest the hanging of Mollah.

The strike started with clashes with law-enforcers, arson, vandalism and crude bomb blasts by Jamaat activists.

A patrol train derailed in northern Rangpur district on Sunday as Jamaat cadres uprooted rail tracks during the strike.

The government deployed additional police in the capital to check the violence during the strike.

Mollah was one of five condemned to death by the International Crimes Tribunal, sentences which the opposition says are aimed at eradicating its leaders.

The sentences have triggered riots and plunged the country into its worst violence since independence. Some 255 people have been killed in street protests since January, when the first verdicts were handed down.