An hours-long attack on an Afghan police special forces base involving car bombs and a firefight killed five policemen and wounded dozens of people, officials said Tuesday, as a top US negotiator called for an end to Afghanistan's bloodshed.

Three suicide bombers detonated their explosives-loaded vehicles targeting the base in the city of Khost near the Pakistan border, Khost police chief Ghulam Daud Tarakhil told AFP, before other gunmen tried to storm the compound.

One suicide bomber detonated his vehicle at the gates of the base early in the morning, while two others blew up their vehicles later during the gun battle between security forces and gunmen, he said.

A fierce firefight that lasted for almost nine hours between the militants and security forces ended with the killing of seven other militants, Tarakhil said.

Afghanistan's interior ministry spokesman Tariq Arian confirmed that the gun battle had ended.

The assault left five policemen dead and wounded 33 other people, including nine civilians, Tarakhil added.

Map of Afghanistan locating Khost where a car bomb attack on a police base followed by a gun battle killed two policemen and wounded dozens of people on Tuesday
Map of Afghanistan locating Khost where a car bomb attack on a police base followed by a gun battle killed two policemen and wounded dozens of people on Tuesday AFP / STAFF

No group immediately claimed responsibility for the attack.

Restive Khost province is home to active Taliban insurgents and also Al-Qaeda fighters, officials say.

Further north, three civilians were killed and 10 others were wounded in a separate attack Tuesday when a "sticky bomb" attached to a car exploded near Kabul airport, police said.

Violence has raged across Afghanistan in recent weeks even as the Taliban and Afghan government remain engaged in peace talks to end the country's long-running conflict.

A wounded man receives medical treatment at a hospital after a car bomb attack on an Afghan police base in Khost province
A wounded man receives medical treatment at a hospital after a car bomb attack on an Afghan police base in Khost province AFP / FARID ZAHIR

Afghan and US officials have repeatedly warned that the rising bloodshed is threatening the talks being held in Qatar since last month.

Zalmay Khalilzad, the US official who negotiated a deal with the Taliban in February to withdraw American forces from Afghanistan by May next year, was again travelling to Qatar to push the two sides to rein in violence.

"The window to achieve a political settlement will not stay open forever," Khalilzad said on Twitter.

"Afghans are dying at a high rate, and regional spoilers are using Afghans as cannon fodder for their illegitimate objectives. Bloodshed must end."

In a separate statement, the US Department of State said Khalilzad will try to persuade the two sides to "accelerate their efforts and agree to a political roadmap" that ends the conflict.

"The sides urgently need an agreement on a reduction of violence leading to a permanent and comprehensive ceasefire," it said.

The United Nations Assistance Mission in Afghanistan (UNAMA) said in a report released Tuesday that the pace of civilian casualties has failed to slow since talks began September 12.

"Peace talks will need some time to help deliver peace," UNAMA chief Deborah Lyons said in the report.

"But all parties can immediately prioritise discussions and take urgent, and frankly overdue, additional steps to stem the terrible harm to civilians."

UNAMA added however that the overall civilian casualty figure had dropped by around 30 percent in the first nine months of 2020 compared to the corresponding period last year.

The first nine months of this year saw 2,177 civilians killed and 3,822 wounded, the report said.

The majority of the civilian casualties, about 58 percent, were caused by "anti-government elements" like the Taliban and Islamic State group, it said.

Afghan security forces were responsible for 23 percent of all civilian casualties, many killed in air strikes and ground engagements.