Twenty people were killed in the latest bout of violence as the largest Islamic party Jamaat-e-Islami declared a nationwide strike to denounce the trials.
In the northern district of Bogra more than 10,000 Jamaat supporters armed with sticks and home-made bombs attacked 12 police stations, torching four of them and two government offices, police said.
"They came from the villages and attacked the stations at dawn. Nine people were killed in Bogra district including four who were killed in Shahjahanpur (town)," police Inspector Shamsul Haq told AFP.
Troops have been deployed in Shahjahanpur to strengthen security, he said. Video footage also showed troops in the area.
Six people were shot dead in the northwestern town of Panchbibi after security officials opened fire at about 12,000 protesters, district chief Mohammad Yasin said.
"The forces fired after they were besieged by the protesters for about two hours. They were armed with sticks, machetes and home-made sharp weapons," he told AFP, adding at least 70 people were injured, many by bullets.
A policeman was beaten to death by protesters in a western district.
The death toll in the clashes over the war crimes verdicts has risen to 76 since the first ruling was announced on January 21, police said, including 60 killed in the four days since Jamaat's vice president was sentenced to death.
Delwar Hossain Sayedee was Thursday found guilty of murder, religious persecution and rape during the 1971 independence war against Pakistan.
The sentence triggered violent clashes across the country between rampaging Jamaat supporters and police.
The 73-year-old firebrand preacher was the third person to be convicted by the war crimes tribunal. Jamaat says the process is an attempt by the ruling party to settle scores and not about delivering justice.
The Islamic party called for two days of nationwide strikes starting Sunday to protest at the verdicts and the killing of its activists by police.
Security was tight in the capital Dhaka with around 10,000 policemen on patrol and shops and schools closed. Inter-city motorways and roads in Dhaka and the port city of Chittagong were empty.
The latest clashes were also fuelled by rumours that images of Sayedee's face were reflected off the surface of the moon, leading many Islamists to assert that he was innocent, Inspector Shamsul Haq of Bogra told AFP.
"Some imams have used this rumour to mobilise villagers against police," he said.
The government has banned rallies and gatherings in at least four towns in the north to quell violence, police said.
The United States and United Nations have appealed for calm while the New York-based Human Rights Watch has urged the government and Jamaat to act urgently to stem further acts of violence.
On Saturday minority groups appealed to the government for increased security after a series of attacks on Hindu temples and houses by Jamaat supporters, in which one Hindu man was killed. Jamaat denied they were behind the attacks.
An inter-city train was torched, allegedly by protesters, late Saturday.
The war crimes trials of a dozen leaders from Jamaat and the main opposition Bangladesh Nationalist Party have opened old wounds and divided the nation, with the opposition accusing the government of staging a witch-hunt.
The government, which says the war claimed three million lives, rejects the claims and accuses Jamaat leaders of being part of pro-Pakistani militias blamed for much of the carnage during the war.
Independent estimates put the death toll from the war at between 300,000 and 500,000.