Police have banned all rallies in the Bangladeshi capital, Dhaka, a day after clashes between the police and protesters left at least 27 people dead.
The country's main opposition parties have called a two-day nationwide shutdown from Wednesday to protest against what they describe as the "mass killing" of protesters in a crackdown by security forces.
The Bangladesh Nationalist Party (BNP) and its Islamist allies called the strike after claiming that hundreds of people were killed on Sunday and early Monday, when police broke up a mass rally in central Dhaka.
"We have called two days of nationwide strike to protest the mass killing of Hifajat-e-Islam workers and supporters on Sunday and Monday," BNP spokesman Khandaker Mosharraf told the AFP news agency on Tuesday.
The strike is set to begin at 6am local time (01:00 GMT) on Wednesday and end at 6pm on Thursday, Mosharraf added.
On Monday, supporters of the Hifazat-e-Islam organisation who are demanding an anti-blasphemy law, blocked roads with burning tires in clashes that lasted for more than five hours and left more than 100 people injured.
Police said they used sound grenades, water cannon, tear gas and rubber bullets to disperse at least 70,000 protesters who were camped at the commercial district of Motijheel in the capital.
"We were forced to act after they unlawfully continued their gathering at Motijheel. They attacked us with bricks, stones, rods and bamboo sticks," Dhaka police spokesman Masudur Rahman AFP.
Violence also flared up at Hathazari, a town just outside the southern city of Chittagong, as well as in the southern coastal district of Bagerhat.
Dozens of demonstrators were arrested, while the leader of the protests, 93-year-old Allama Shah Ahmad Shafi, was put on a plane bound for Chittagong and the deputy chief was detained in the capital.
Police said that Shafi had not been arrested.
According to Al Jazeera correspondent, whom we are not naming due to reporting restrictions, said Hefazat-e-Islam has called for nationwide shutdown on May 12.
The turmoil comes as the government struggles to deal with outrage over the collapse of a factory building northwest of Dhaka, where the death toll has crossed 700 since the late April accident.
TV stations off air
Two local television stations - Diganta Television and Islamic TV - which broadcast footage of the raid on Motijheel were forced off the air, journalists at the channels said.
Ban Ki-moon, the UN secretary-general, called for an end to the violence, expressing his sadness at the loss of life, a spokesman said.
Ban "urges political and religious leaders to engage in constructive dialogue and help defuse the tensions," Martin Nesirky, the UN spokesman, said.
Follow in-depth coverage of war crimes trials in Dhaka
The demonstrators demanded mandatory religious education and the end to what they described as an "anti-Islam" policy that calls for gender equality.
Hifazat, a newly created religious group, is demanding the death penalty for all those it says are defaming Islam.
It said it held the mass protest to push a 13-point list of demands which also included a ban on men and women mixing freely together and the restoration of pledges to Allah in the constitution.
Sheikh Hasina Wajed, Bangladesh prime minister, has said the existing laws already have sufficient safeguards to address the protesters' concerns.
She said that the government "will not allow any chaos in the name of Islam, a religion of peace".
The South Asian nation, officially secular with a 90 percent Muslim population, has seen a surge in violence since January, when a court began handing down war crimes verdicts related to the 1971 independence war.
Three leading Islamists have so far been convicted for their role in mass killings during the liberation war, which saw the birth of the new nation of Bangladesh from Pakistan.