Bangladesh Prime Minister Sheikh Hasina's resignation is a "possibility", French news agency AFP reported on Monday, as six more people were killed in some of the worst violence since the birth of the South Asian nation more than five decades ago.

Hasina's resignation is a "possibility", AFP reported citing a senior aide. Reuters could not immediately verify the report. Hasina and her sister had been taken to a "safe shelter" away from her official residence, a government source told Reuters.

"You see, the situation is very volatile. What is happening, I myself don’t know," Law Minister Anisul Huq told Reuters.

Student activists had called for a march to the capital Dhaka on Monday in defiance of a nationwide curfew to press Hasina to resign, a day after deadly clashes across the country killed nearly 100 people.

As protesters began to march in some places, armoured personnel carriers and troops patrolled the streets of the capital, Reuters TV showed. There was little civilian traffic, barring a few motorcycles and three-wheel taxis.

At least six people were killed in clashes between police and protesters in the Jatrabari and Dhaka Medical College areas on Monday, the Daily Star newspaper reported. Reuters could not immediately verify the report.

Police hurled sound grenades in some parts of the city to disperse small groups of protesters, the Bengali language Prothom Alo newspaper reported.

Elsewhere, thousands of protesters had surrounded law enforcement officers stationed in front of a key building, it said.

Army chief General Waker-Uz-Zaman, who was due to address the nation at 2 p.m. local time (0800 GMT) would now do so at 3 p.m. (0900 GMT), an army officer told Reuters. "He is holding talks with some stakeholders, outside the military. That’s why the delay," the officer said.

The military spokesperson's office had earlier said that "the public is requested to refrain from violence and be patient," until the army chief's address, Prothom Alo reported.

Bangladesh has been engulfed by protests and violence that began last month after student groups demanded scrapping of a controversial quota system in government jobs.

That escalated into a campaign to seek the ouster of Hasina, who won a fourth straight term in January in an election boycotted by the opposition.

At least 91 people were killed and hundreds injured on Sunday in a wave of violence across the country of 170 million people as police fired tear gas and rubber bullets to disperse tens of thousands of protesters.

Starting Sunday evening, a nationwide curfew has been imposed, the railways have suspended services and the country's huge garments industry has closed.