The burial was of a victim of violent clashes between the police and protesters on Friday.

At least six people were killed and dozens wounded as explosions rocked the funeral of an Afghan politician's son who died during an anti-government protest over spiralling insecurity in Kabul, raising tensions in a city already on edge.

Witnesses reported three blasts at the burial site of Salim Ezadyar, who was among four people killed on Friday when the protest degenerated into street clashes with police, fuelling anger against the government.

The hilly, wind-swept site was littered with bloodied corpses and dismembered limbs, local television footage showed, with one witness telling AFP that "people were blown to pieces" due to the impact of the blasts.

"So far six dead bodies and 87 wounded people have been brought to Kabul hospitals," Health Ministry spokesman Waheed Majroh told AFP.

The funeral of Salim Ezadyar, the son of an Afghan Senator, was attended by senior government figures including Chief Executive Abdullah Abdullah, but his office told AFP that the latter was unhurt.

No group has so far claimed responsibility for the attack. President Ashraf Ghani condemned the bombings, saying on Twitter: "The country is under attack. We must stay united."

The fresh killings are likely to further polarise a city that has been on edge since a truck bombing on Wednesday in Kabul's diplomatic quarter killed 90 people and wounded hundreds of others, in the deadliest attack on the Afghan capital since 2001.

The bombing highlighted the ability of militants to strike even in the capital's most secure district, home to the presidential palace and foreign embassies that are enveloped in a maze of concrete blast walls.

Hundreds of angry demonstrators calling for Mr. Ghani to step down over spiralling insecurity clashed with police on Friday, prompting officials to beat them back with live rounds in the air, tear gas and water cannon.

City on lockdown

Kabul city was on lockdown on Saturday with armed checkpoints and armoured vehicles patrolling the streets to prevent a repeat of Friday's protests.

Before the blasts at the funeral, authorities had sealed off roads in the centre of the city, citing the threat of new attacks on large gatherings of people.

"We have intelligence reports that our enemies are trying again to carry out attacks on gatherings and demonstrations," Kabul garrison commander Gul Nabi Ahmadzai said earlier Saturday. "We hope that people will stay away from protests."

But dozens of people still gathered on Saturday under a tent close to the presidential palace calling for Mr. Ghani's government to resign, but the assembly was largely peaceful.

"Any government attempt to disrupt our fair and just demonstration will show their complicity with terrorist groups and the perpetrators of Wednesday's attack," said Asif Ashna, a spokesman for the protesters.

"It is the duty of the government to ensure security to the protesters... and the government will be held responsible for any violence."

The United Nations and a host of international allies have urged the protesters for restraint.

"The enemy seeks to manipulate the people's anger and sadness to create division and sow instability," the U.S. embassy said in a statement.

"Now is the time to stand unified and announce to the enemies that Afghans... will not allow cowards to break the resolve to achieve a stable and peaceful nation. The enemies of Afghanistan cannot win. They will not win."