KABUL - Militants stormed a government building in Afghanistan's capital Kabul on Monday, taking civilians hostage as they fought a gun battle against Afghan soldiers, officials said.

The attack began in the afternoon when a suicide bomber blew up a car outside the Ministry of Public Works.

Shooting followed, with hundreds of government employees inside the building, said Interior Ministry official Nasrat Rahimi. No group immediately claimed responsibility.

Rahimi said two militants had been killed but gunmen in a nearby government building were exchanging fire with security forces.

"More than 200 people have been evacuated by the security forces, but many are still being held as hostages by the militants," he said.

At least four people wounded in the clashes were taken to hospital, according to a spokesman for the health ministry.

An official working in a nearby government building said employees had locked themselves in their offices after hearing the explosions and gunfire.

Attacks on government offices are frequent and are generally carried out by the Islamist Taliban, who are fighting to expel foreign forces from strategic provinces, topple the Western-backed government and restore their version of hardline Islamic law.

The 17-year-old war with the Taliban has seen both fighting and diplomacy intensify in recent months.

On Thursday, an official said US President Donald Trump was planning to withdraw at least 5,000 of the 14,000 US troops in Afghanistan, a day after Trump unexpectedly announced that US troops in Syria would be withdrawn.

The United States went to war in Afghanistan in 2001 in the wake of the Sept. 11, 2001 attacks on the World Trade Center in New York and the Pentagon in Washington, seeking to oust the Taliban militants harbouring Saudi-raised militant Osama bin Laden, who led plans to carry out the attacks.

At present, American troops make up the bulk of the Resolute Support mission to train and advise Afghan forces fighting the Taliban and the Islamic State militant group. Others are part of a US-led counter-terrorism mission.

The prospect of a US drawdown has triggered widespread uncertainty in war-torn Afghanistan.

With security deteriorating, Afghan President Ashraf Ghani on Sunday replaced his defence and interior ministers with two uncompromising opponents of the Taliban.

Reuters