Bangladeshi Prime Minister Sheikh Hasina's 15-year rule of the country ended on Monday as she fled weeks of deadly protests and the military announced it would form an interim government.

Hasina had sought since early July sought to quell nationwide protests against her government, but she fled after a brutal day of unrest on Sunday in which nearly 100 people died.

In a broadcast to the nation on state television, Bangladesh's army chief Waker-Uz-Zaman said on Monday Hasina had resigned and the military would form an interim government.

"The country has suffered a lot, the economy has been hit, many people have been killed -- it is time to stop the violence," Waker said.

"I hope after my speech, the situation will improve."

Hasina, 76, fled the country by helicopter, a source close to the leader told AFP shortly after protesters had stormed her palace in Dhaka.

The source said she left first by motorcade but then was flown out, without saying her destination.

Jubilant crowds had waved flags, some dancing on top of a tank in the streets on Monday morning before hundreds broke through the gates of Hasina's official residence.

Bangladesh's Channel 24 broadcast images of crowds running into the compound, waving to the camera as they celebrated.

Others smashed a statue of Hasina's father Sheikh Mujibur Rahma, the country's independence hero.

Before the protesters had stormed the compound, Hasina's son urged the country's security forces to block any takeover.

"Your duty is to keep our people safe and our country safe and to uphold the constitution," her son, US-based Sajeeb Wazed Joy, said in a post on Facebook.

"It means don't allow any unelected government to come in power for one minute, it is your duty."

Security forces had supported Hasina's government throughout the unrest, which began last month against civil service job quotas then escalated into wider calls for her to stand down.

At least 94 people were killed on Sunday, including 14 police officers, in the deadliest day of the unrest.

Protesters and government supporters countrywide battled each other with sticks and knives, and security forces opened fire.

The day's violence took the total number of people killed since protests began in early July to at least 300, according to an AFP tally based on police, government officials and doctors at hospitals.

The military declared an emergency in January 2007 after widespread political unrest and installed a military-backed caretaker government for two years.

Hasina then ruled Bangladesh from 2009 and won her fourth consecutive election in January after a vote without genuine opposition.

Her government was accused by rights groups of misusing state institutions to entrench its hold on power and stamp out dissent, including through the extrajudicial killing of opposition activists.

Demonstrations began over the reintroduction of a quota scheme that reserved more than half of all government jobs for certain groups.

The protests escalated despite the scheme having been scaled back by Bangladesh's top court.

Soldiers and police with armoured vehicles in Dhaka had barricaded routes to Hasina's office with barbed wire on Monday morning, but vast crowds flooded the streets, tearing down barriers.

The Business Standard newspaper estimated as many as 400,000 protesters were on the streets but it was impossible to verify the figure.

"The time has come for the final protest," said Asif Mahmud, one of the key leaders in the nationwide civil disobedience campaign.

In several cases, soldiers and police did not intervene to stem Sunday's protests, unlike during the past month of rallies that repeatedly ended in deadly crackdowns.

In a hugely symbolic rebuke of Hasina, a respected former army chief demanded the government "immediately" withdraw troops and allow protests.

"Those who are responsible for pushing people of this country to a state of such an extreme misery will have to be brought to justice," ex-army chief General Ikbal Karim Bhuiyan told reporters Sunday.

The anti-government movement had attracted people from across society in the South Asian nation of about 170 million people, including film stars, musicians and singers.