Police arrested five students Saturday on charges of murdering an anti-Islamist blogger, as four people were killed in fresh protests over the sentencing to death of an Islamic party leader for war crimes.
The students allegedly confessed to hacking to death blogger Ahmed Rajib Haider after he helped organise protests against leaders of the biggest Islamic party, Jamaat-e-Islami, who are being tried by a war crimes court, police said.
The students, all enrolled at the elite private North South University, targeted Haider, 35, "because of his allegedly blasphemous writings against Islam and the Prophet Mohammed," Dhaka police deputy commissioner Masudur Rahman said.
"They tracked him by his Facebook account" and "on the day of the murder they played cricket in front of his home and waited for his return", he told AFP.
The arrests came as police firing claimed four lives during street protests over the sentencing of Islamist leaders for crimes committed in the 1971 independence war.
The deaths bring the total toll of those killed since the tribunal delivered its first verdict on January 21 to 57, according to police.
The trials of a dozen Jamaat and main opposition Bangladesh Nationalist Party leaders have opened old wounds and divided the nation.
More unrest looms on Sunday in the impoverished South Asian nation, when Jamaat is due to hold a nationwide general strike to protest against the trials.
In Saturday's violence police said they killed three people outside the port city of Chittagong when they opened fire on Islamists protesting against the death penalty given earlier in the week to Jamaat vice president Delwar Hossain Sayedee.
The 73-year-old firebrand preacher was the third person to be convicted by the tribunal, whose verdicts have been met by outrage from Islamists who say the process is more about settling scores than delivering justice.
Another protester was shot dead when border guards fired on more than 1,000 Jamaat demonstrators in northern Joldhaka town, police said.
Police and media reported clashes between Jamaat supporters and police in at least half a dozen towns and cities, while in Dhaka police said they fired rubber bullets and gas at protesters.
The government, which says the 1971 independence war claimed three million lives, accuses Jamaat leaders of being part of pro-Pakistani militias blamed for much of the carnage -- charges they deny.
Independent estimates put the death toll from the war in which Bangladesh won its independence from Pakistan at a much lower 300,000 to 500,000.
The fresh violence came a day after the United States called for calm.
"While engaging in a peaceful protest is a fundamental democratic right, we believe violence is never the answer," US State Department deputy acting spokesman Patrick Ventrell told reporters in Washington.