A demonstration in downtown Kabul has turned violent, as police fired on rock-throwing protesters demanding better security in the Afghan capital in the wake of a powerful truck bomb attack that killed at least 80 people.

Several demonstrators were killed and police injured, authorities said.

More than 1,000 people demonstrated as Afghans mourned the victims of the massive truck bomb that wounded 450 people on Wednesday.

It was one of the worst extremist attacks since the drawdown of foreign forces in 2014 and raised fears about the government’s ability to protect its citizens nearly 16 years into a war with insurgents.

Police fired their weapons into the air as a warning at first as about 100 of the demonstrators rushed toward them, some throwing rocks.

Kabul’s unanswered questions

Kabul is reeling after one of the deadliest attacks in the 16-year Afghanistan intervention, and still grappling with key unanswered questions. Who did it? Why? Will it change anything?

As the protesters attempted to move closer to the Presidential Palace, police sprayed them with hoses from a water tanker and later fired tear gas.

Reports of casualties varied, with Abdul Hafiz Mansur, a member of Parliament from Kabul, saying eight protesters were shot dead by police.

However, General Hassan Shah Froogh, Kabul police chief, said two protesters were killed and 25 police were wounded by rocks thrown from demonstrators.

He said several protesters were carrying weapons and shooting towards police as four armed demonstrators were arrested.

Shopkeeper Mohammad Anwar said four members of his family were killed in the bombing and he wanted a change of leadership.

“We are calling on President Mohammad Ashraf Ghani to resign,” he said.

Demonstrators also called for Chief Executive Abdullah Abdullah to step down.

Mr Ghani’s office issued a statement expressing condolences for the families of people who died in the protest but urged protesters not to allow “other opportunists” to use their demonstrations as an opportunity for violence for their own goals.

“The Government of Afghanistan assures that the culprits of crimes against people will be brought to justice,” the statement read.

“Also the leadership of the Government promises that all those security officials who have neglected in their duty to provide security for the people will be punished in accordance to the Afghan laws and will be brought to justice.”

Most of the casualties from the truck bombing were civilians, including women and children, officials have said.

But the dead also included Afghan security guards at the facilities, including the US embassy, and 11 American contractors were wounded — although none with life-threatening injuries, a US State Department official said.

No one has claimed responsibility for the attack, which came in the first week of the Muslim holy month of Ramadan.

—with AP