A foreign national was killed and at least five other people wounded in a grenade attack on a United Nations vehicle in Kabul on Sunday, an Afghan official said.

The attack happened on a road frequently used by UN traffic shuttling workers between central Kabul and a large UN compound on the outskirts of the capital. "At around 6:20 pm (1350 GMT) a grenade was hurled at a UN vehicle," interior ministry spokesman Nasrat Rahimi said.

Aside from the one fatality, Rahimi said five other people - including two Afghan staff - were wounded. The nationalities of the other victims were not released.

A UN official did not immediately return a message seeking comment, and no group has yet claimed responsibility for the attack.

The blast comes during what has been a period of relative and uneasy calm in Kabul, where large-scale attacks have dropped over recent weeks.

The comparative lull followed a blood-stained presidential campaign season that ended with a general election nearly two months ago.

But Afghans are still waiting for the results of that September 28 poll, with a recount bogged down by various technical difficulties and complaints from main candidates.

Additionally, Afghans are waiting to see what might happen next in negotiations between the Taliban and the US.

President Donald Trump in September ended those yearlong talks as Taliban violence continued, but on Friday he suggested to US broadcaster Fox News that negotiations could be getting underway again.