(UPDATE) DHAKA — Soldiers were patrolling Bangladeshi cities on Saturday to quell growing civil unrest sparked by student demonstrations, with riot police firing on protesters who defied a government curfew.

This week's violence has killed at least 115 people so far, according to an Agence France-Presse (AFP) count of victims reported by police and hospitals, and poses a monumental challenge to Prime Minister Sheikh Hasina's autocratic government after 15 years in office.

A government curfew went into effect at midnight and the premier's office asked the military to deploy troops after police again failed to subdue widespread mayhem.

"The army has been deployed nationwide to control the law-and-order situation," armed forces spokesman Shahdat Hossain told AFP.

The curfew will remain in effect until at least 10 a.m. on Sunday, private broadcaster Channel 24 reported.

Streets of the capital Dhaka were almost deserted at daybreak, with troops on foot and in armored personnel carriers patrolling the sprawling megacity of 20 million.

Thousands returned to the streets later in the day in the residential neighborhood of Rampura, with police firing live rounds at the crowd and wounding at least one person.

"Our backs are to the wall," protester Nazrul Islam, 52, told AFP at the scene. "There's anarchy going on in the country.... They are shooting at people like birds."

Hospitals have reported a growing number of gunshot deaths to AFP since Thursday.

"Hundreds of thousands of people" had battled police across the capital on Friday, police spokesman Faruk Hossain told AFP.

"At least 150 police officers were admitted to the hospital. Another 150 were given first-aid treatment," he said, adding that two officers had been beaten to death. "The protesters torched many police booths.... Many government offices were torched and vandalized."

A spokesman for Students Against Discrimination, the main group organizing the protests, told AFP that two of its leaders had been arrested since Friday.

A second senior official from the main opposition Bangladesh Nationalist Party (BNP) was arrested in the early hours of Saturday, party spokesman Sairul Islam Khan told AFP.

Hasina had been due to leave the country on Sunday for a planned diplomatic tour but abandoned her plans after a week of escalating violence.

"She has canceled her Spain and Brazil tours due to the prevailing situation," her Press Secretary Nayeemul Islam Khan told AFP.

'Not about students anymore'

Near-daily marches this month have called for an end to a quota system that reserves more than half of civil service posts for specific groups, including children of veterans from the country's 1971 liberation war against Pakistan.

Critics say the scheme benefits children of pro-government groups that back Hasina, 76, who has ruled the country since 2009 and won her fourth consecutive election in January after a vote without genuine opposition.

Hasina's government is accused by rights groups of misusing state institutions to entrench its hold on power and stamp out dissent, including the extrajudicial killing of opposition activists.

Since the first deaths on Tuesday, protesters have begun demanding Hasina leave office.

"It's not about the rights of the students anymore," business owner Hasibul Sheikh, 24, told AFP at the scene of the Rampura protest.

"We are here as the general public now," he added. "Our demand is one point now, and that's the resignation of the government."

Hospitals and police reported an additional 10 deaths to AFP on Saturday from clashes the previous day, with 105 other deaths reported since Tuesday.

Police fire was the cause of more than half of the deaths reported so far this week, based on descriptions given to AFP by hospital staff.

"The rising death toll is a shocking indictment of the absolute intolerance shown by the Bangladeshi authorities to protest and dissent," Babu Ram Pant of Amnesty International said in a statement.