image sourceReutersimage captionUS troops have been on high alert as the deadline for withdrawal approaches

The US military has said it is investigating after at least nine Afghan civilians were reportedly killed in a drone strike which aimed to prevent an attack on Kabul airport.

The strike targeted a vehicle carrying at least one person associated with the Afghan branch of the Islamic State group, US Central Command said.

It is unclear how the civilians died.

Information being shared by Kabul residents suggest four young children were among the casualties.

A relative told US network CNN that all nine people were members of one family.

A US Central Command statement acknowledged there were a number of "substantial and powerful subsequent explosions" after the strike hit the car that was being targeted.

It said the explosions suggested there had been "a large amount of explosive material inside, that may have caused additional casualties".

The US has been on high alert since a suicide bomber killed more than 100 civilians and 13 US troops outside the airport last Thursday. A local branch of the so-called Islamic State claimed responsibility.

Many of those killed had been hoping to board one of the evacuation flights leaving the city, which fell to the Taliban on 15 August.

The US had repeatedly warned of an increase in attacks as 31 August – the date set for the Americans' withdrawal from Afghanistan – drew closer.

On Monday, a US anti-missile system intercepted rockets flying over the capital towards the airport, an official told Reuters news agency.

Video and pictures carried by local news outlets showed smoke wafting across the rooftops of Kabul, and what appeared to be a burning car on a street.

کابل – گواهان رویداد می‌گویند چندین موشک‌ با استفاده از یک موتر از منطقه خیرخانه به سمت فرودگاه کابل شلیک شده اند.

تاهنوز از تلفات و خسارات جزییات در دست نیست.#ArianaNews

— Ariana News (@ArianaNews_) August 30, 2021
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The White House said President Joe Biden was briefed on the rocket attack.

"The President was informed that operations continue uninterrupted at HKIA (Kabul airport), and has reconfirmed his order that commanders redouble their efforts to prioritize doing whatever is necessary to protect our forces on the ground," White House press secretary Jen Psaki said in a statement.

No US or Afghan casualties have been reported so far from Monday's incident.

The United States has installed an anti-rocket and mortar system to protect the airport from further attacks.

media captionWatch: Bodies of US troops returned to America

Later on Monday, British ministers and officials will be taking part in a number of international meetings aimed at defining a joint approach to the Taliban in Afghanistan.

Foreign Secretary Dominic Raab will hold talks with his counterparts from the G7 group of wealthy countries, as well as Nato and Qatar.

At the United Nations in New York, France and Britain are expected to propose a Security Council resolution calling for a safe zone in Kabul to protect people trying to leave the country.