At least 88 people have been killed in Bangladesh amid worsening clashes between police and anti-government protesters.

The unrest comes as student leaders have declared a campaign of civil disobedience to demand that Prime Minister Sheikh Hasina step down.

Thirteen police officers were killed when thousands of people attacked a police station in the district of Sirajganj, police said.

The student protest started with a demand to abolish quotas in civil service jobs last month, but have now turned into a wider anti-government movement.

Both police and supporters of the governing party were seen shooting at anti-government protesters with live ammunition. Police also used tear gas and rubber bullets.

A nighttime curfew has been in place since 18:00 (12:00 GMT).

On Sunday Law and Justice Minister Anisul Huq told the BBC’s Newshour programme that authorities were showing “restraint”.

“If we had not shown restraint there would have been a bloodbath. I guess our patience has limits,” he added.

In the capital, Dhaka, access to internet on mobile devices has been suspended.

An official from the Bangladesh Telecommunication Regulatory Commission (BTRC) official told BBC Bengali that 4G internet service in the Dhaka area had stopped for now, but broadband services would continue.

Without 4G and 3G people cannot communicate using the internet on their mobile devices. The source did not say when internet services would return to normal.

Deaths and injuries have been reported across the country, including the northern districts of Bogra, Pabna and Rangpur.

Thousands of people gathered in a main square in Dhaka and there have been violent incidents in other parts of the city.

In some places, supporters of the governing Awami League are said to be clashing with anti-government protesters.

“The whole city has turned into a battleground,” a policeman, who asked not to be named, told AFP news agency. He said a crowd of several thousand protesters had set fire to cars and motorcycles outside a hospital.

Students Against Discrimination, a group behind the anti-government demonstrations, has called on the prime minister to step down.

The group announced a nationwide disobedience movement starting from Sunday, urging citizens not to pay taxes or any utility bills. The students have also called for a shutdown of all factories and public transport.