Bangladesh police have fired rubber bullets at protesters, after the execution of a top Islamist leader heightened tensions in a country reeling from the murders of several secular and liberal activists.

The violence came as police charged Khaleda Zia, leader of the main Bangladesh opposition, with masterminding arson attacks during anti-government protests last year – the latest in a string of charges she claims are politically motivated.

Hours earlier her main political ally, Motiur Rahman Nizami, leader of the Jamaat-e-Islami party, was hanged at a Dhaka jail for the massacre of intellectuals during the 1971 independence war with Pakistan.

Police said hundreds of Nizami’s supporters attacked them with stones in the northwestern city of Rajshahi, where a liberal professor was killed by suspected Islamists last month.

“There were 500 Jamaat activists who were protesting the execution. We fired rubber bullets as they became violent,” Rajshahi police inspector Selim Badsah told AFP, adding that about 20 were arrested.

Jamaat and ruling party supporters also clashed in Chittagong, where about 2,500 Islamists attended a service for the executed leader, the port city’s deputy police chief, Masudul Hasan, told AFP.

Security was tight across the country, with checkpoints erected on main roads in Dhaka to deter violence and thousands of police patrolling the capital.

Nizami, a 73-year-old former government minister, was the fifth and most senior opposition figure executed since the secular administration set up a controversial war crimes tribunal in 2010.

Pakistan’s foreign ministry said on Wednesday it was “deeply saddened” by the hanging.

Security was also stepped up at Nizami’s ancestral district of Pabna, where his body was taken under armed escort for burial in his family’s grave.

Jamaat called a nationwide strike for Thursday in protest against Nizami’s execution, saying the charges against him were false and aimed at eliminating the party’s leadership.

Executions of Jamaat officials in 2013 triggered the country’s deadliest violence in decades. Around 500 people were killed, mainly in clashes between Islamists and police.

But another wave of bloodshed is considered unlikely following a major crackdown by prime minister Sheikh Hasina’s government that has seen tens of thousands of Jamaat supporters detained.

Secular protesters cheered the midnight hanging, and hundreds gathered outside the jail and at a square in central Dhaka overnight to celebrate what they described as a historic moment.

Mubashar Hasan, an assistant professor at Bangladesh’s University of Liberal Arts, said Tuesday’s execution may sound the death knell for the already embattled Jamaat.

“With the execution of Nizami, the Jamaat leadership who revived the fortune of the party in the post-1971 period are now almost gone,” he said.

The hanging comes amid a wave of murders by suspected Islamists, with an atheist student, two gay rights activists, a professor, a Hindu tailor and a Sufi Muslim leader hacked to death since last month.

Islamic State and a Bangladesh branch of al-Qaida have claimed responsibility for several murders, but the government blames homegrown extremists and accuses the opposition of trying to destabilise the country.

Opposition leader Zia, the premier’s bitter rival, was charged earlier this year over a deadly fire-bombing of a bus in Dhaka during a 2015 nationwide transport blockade aimed at toppling the government.

Nizami took over as Jamaat leader in 2000 and played a key role in the victory of an Islamist-allied government in the 2001 general election.

The 1971 conflict, one of the bloodiest in world history, led to the creation of an independent Bangladesh from what was then East Pakistan.

Prosecutors said Nizami was responsible for setting up the pro-Pakistani Al-Badr militia, which killed top writers, doctors and journalists in the most severe chapter of the war.

He was convicted in October 2014 by the international crimes tribunal, which has sentenced more than a dozen opposition leaders for war crimes in trials criticised by rights groups.