The sexual assault of a student at a top university in Bangladesh has triggered angry protests in the capital Dhaka, with demonstrators calling for the death penalty for all the convicted rapists.

Demonstrators on Monday linked arms and marched along main roads in Dhaka, halting traffic to demand the perpetrator's arrest within 24 hours.

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Signs held up in the protest included messages such as: "No mercy to rapist" and "Please tell me, am I next?"

"Rape is an unforgivable offence. In Bangladesh, the punishment for rape is very slow," said Shahela, a demonstrator who, like the 21-year-old victim of Sunday's attack, is a student at Dhaka University.

"We want quick executions for the perpetrators so that others are deterred from committing such crimes," she said.

Nurul Haque Nur, vice president of Dhaka University Central Students' Union, said: "Dhaka University is considered the supreme educational institute of the country. It is very shameful that a student of that institute was raped."

"We demand that all the rape cases in the country including this one are processed under a speedy tribunal and that the rapists are brought to justice," he said.

Jannat Ul Firdous, a Dhaka University student, said rapists must be killed.

"We want nothing but the rapists' execution by hanging. How is it possible that women can't move freely in an independent country? We can't just passively witness the assaults of rapists. We demand that the rapists are hanged," the protester said.

Police said about 1,500 students joined the protests, which remained peaceful. AFP news agency estimated that twice as many people joined the rally.

Sunday's assault

The victim in Sunday's attack was travelling to a friend's home when she was gagged, taken to a remote area in Dhaka's outskirts and sexually assaulted.

The victim was taken to Dhaka Medical College and Hospital at about midnight on Sunday, and is being treated there.

"We are working to arrest [the attacker]," Sazzadur Rahman, senior police official, told AFP news agency.

Local rights group Ain o Salish Kendra said there were 1,413 reported rape cases in Bangladesh last year, double the number recorded in 2018. Dozens of victims were killed while 10 committed suicide after they were attacked.

Nationwide protests gripped Bangladesh in April after a 19-year-old student who accused her seminary's head teacher of sexual harassment was doused in kerosene and set on fire.

Sixteen people were later sentenced to death over the attack, including the teacher.