LONDON: Britain's defence ministry said it was working urgently to establish what had happened at Kabul airport following reports of an explosion.

"We are working urgently to establish what has happened in Kabul and its impact on the ongoing evacuation effort," the defence ministry said on Twitter.

Explosion outside Kabul airport, casualties unclear: Pentagon

"Our primary concern remains the safety of our personnel, British citizens and the citizens of Afghanistan. We are in close contact with our US and other NATO allies at an operational level on the immediate response to this incident."