At least three people died and other 60 have been injured during clashes between police and Islamist protesters of Hefajat-e-Islam in the Bangladeshi capital Dhaka.
Up to half a million protesters gathered in Dhaka, where rioters set fire to shops and vehicles as police fought to contain them.
Thousands of activists from Hefajat-e-Islam blocked highways, isolating Dhaka from other parts of the country.
They are calling for those who insult Islam to face the death penalty.
They also want greater segregation of men and women, as well as the imposition of stricter Islamic education.
Hefajat-e-Islam’s opposition to a national development policy for women has angered women’s groups.
The group draws its strength from the country’s madrassahs, or religious schools.
But the government, which describes Bangladesh as a secular democracy, has rejected the group’s demand for a new law on blasphemy.
PM Sheikh Hasina said current legislation was adequate.
Chanting “Allahu Akbar!” (“God is greatest!”) and “One point! One demand! Atheists must be hanged”, the activists marched down at least six main roads, AFP news agency reported.
They headed for Motijheel, Dhaka’s main commercial district.
The area around the city centre’s largest mosque turned into a battleground as police reacted to stone-throwing rioters with tear gas, rubber bullets and truncheons.
Three people were killed with at least one dying of gunshot wounds.
Reports spoke of some 60 people being injured, including two local TV journalists.
A Hefajat-e-Islam activist, Hossain Soliman Abdullah, said the main aim of the protest was to press for the implementation of a 13-point demand inspired by the Koran.
Dhaka’s Daily Star newspaper reports that the group hired at least 3,000 vehicles, including buses, lorries and minibuses to bring demonstrators into the capital, while others travelled there by train.
On Friday, PM Sheikh Hasina said the government had already met many of the group’s demands.
“Many of these have already been implemented while some are in the process,” she was quoted as telling the Daily Star.
Sheikh Hasina said the government had already arrested four bloggers for making “derogatory comments” against the Prophet Muhammad and they would be prosecuted if found guilty.
Muslims make up nearly 90% of Bangladesh’s population with the rest mostly Hindus.