More than 20 people have been killed and dozens more injured in a new round of violence in Bangladesh as police fired tear gas and lobbed stun grenades to disperse tens of thousands of protesters who returned to the streets to ask Prime Minister Sheikh Hasina to resign.

The deaths were reported by the police and doctors on Sunday in the capital Dhaka and in the northern districts of Bogura, Pabna and Rangpur, as well as in Magura in the west, Comilla in the east, and Barisal and Feni in the south.

The demonstrators were demanding Hasina’s resignation after earlier protests in July that began with students calling for an end to a quota system for government jobs escalated into violence that left more than 200 people dead.

Protesters called for “non-cooperation,” urging people not to pay taxes and utility bills and not show up for work on Sunday, a working day in Bangladesh. Offices, banks and factories opened, but commuters in Dhaka and other cities faced challenges getting to work.

The protesters attacked Bangabandhu Sheikh Mujib Medical University, a major public hospital in Dhaka’s Shahbagh area, torching several vehicles.

In Dhaka’s Uttara neighborhood, police fired tear gas to disperse hundreds of people who blocked a major highway.

Protesters attacked homes and vandalised a community welfare office in the area, where hundreds of ruling party activists took up positions. Some crude bombs were detonated and gunshots were heard, witnesses said.

The protests began last month as students demanded an end to a quota system.

The unrest, which spurred the government to shut down internet services, is its biggest test since January when deadly protests erupted after Hasina’s Awami League party won a fourth straight term in elections boycotted by the main opposition Bangladesh Nationalist Party (BNP).

The protests have now grown into a wider antigovernment movement across the South Asian nation of some 170 million people. At least 11,000 people have been arrested in recent weeks.

Critics of Hasina, along with human rights groups, have accused her government of using excessive force to stamp out the movement, a charge it denies.