The Bangladesh Daily Star reported at least 33 people, including four policemen, had died and scores more injured as supporters of Jamaat-e-Islami leader Delawar Hossain Sayeedi clashed with security forces and others across the country.
Sayeedi, who has denied all the charges against him, was ordered hanged Thursday by a tribunal set up to investigate crimes committed during the 1971 war of independence that led the eastern wing of Pakistan to secede and emerge as independent Bangladesh. The 73-year-old was found guilty of charges that included mass murder, torture and rape.
CNN placed the death toll in the riots at 37.
There have been protests for weeks by members of the Jamaat and its student wing against the tribunal, which they claim are part of a political vendetta by the government. There have also been protests by those who support the tribunal, seeking tougher sentences against the accused.
The tribunal was set up in 2010 to try some of the local groups who allegedly opposed the 1971 freedom war and collaborated with the Pakistani army in aiding the killings, rapes and other atrocities.
The Star quoted the Islamist group and its student wing Islami Chhatra Shibir as claiming that 20 of the dead in the clashes were their members.
The report said even prior to the tribunal's verdict, Jamaat-Shibir men were out on the streets to enforce a daylong shutdown.
In the capital Dhaka, there were a number of bomb explosions in several areas and the protesters set fire to a number of police vehicles, the Star reported.
The port city of Chittagong was one of the worst affected cities, where about 20 people reportedly died.
Supporters of Sayeedi also targeted the minority Hindu community in several cities including Chittagong, Rangpur, and Sylhet, damaging at least six Hindu temples and setting fires to several Hindu homes and businesses, the report said.
"We ran for our lives leaving everything behind. I was only seven during the Liberation War in 1971, but it didn't feel this insecure even then," one Hindu was quoted as saying.
CNN reported at least two of the police officers were beaten to death on the streets of one of the affected cities.
Home Affairs Minister Shamsul Haque was quoted as telling reporters paramilitary troopers had been summoned to patrol the troublesome cities as part of heightened security. The government also has banned rallies and gatherings in some districts.
Sayeedi, whose sentencing will be appealed, had been accused of working with a Pakistani terrorist group during the 1971 war and committing atrocities such as forcibly converting Hindus to Islam. He also was accused of forming a small group during the war to loot and seize property of Bengali Hindus and other supporters of Bangladesh's independence.
He is the third and the most senior militant leader to be convicted so far by the tribunal.
Earlier in February, the tribunal gave a life sentence to Abdul Kader Mullah. In January, Jamaat member Abul Kalam Azad was sentenced, in absentia, to death.
Since these verdicts, Bangladesh's parliament has amended a law to allow appeal of the tribunal's decisions.
Bangladesh, formerly called East Pakistan, became an independent republic in 1971 after a nine-month war against the Pakistani army. Some estimates say as many as 3 million people died and tens of thousands of women were raped and attacked during the war.
The tribunal does not conform with international standards, human rights groups have said.