Image copyright Reuters Image caption The attack on the counter-narcotics building comes against the backdrop of a hotly-disputed election

A suicide bomber has killed four people, including at least three foreign security guards, in an attack outside Kabul airport, officials say.

The Taliban said they carried out the bombing, which targeted a key counter-narcotics building.

Four insurgents also died, officials say. There is no word on the nationalities of the foreigners killed.

The attack comes days after security forces repelled an attack on Kabul airport by the Taliban.

In a separate attack on Tuesday, a roadside bomb injured a civilian close to the Afghan meteorology department near the civilian entrance of the airport.

'Invader forces'

Heavily armed militants attacked the counter-narcotics building with grenades and automatic weapons.

Police say the bomber rode a motorcycle and detonated his explosives outside the main entrance, located close to a foreign military base 2km (1.2 miles) from the main runway.

In addition to the security guards and insurgents killed in the exchange, at least six other guards were wounded.

Image copyright AFP Image caption Broken glass and debris in the aftermath of the attack lay strewn across the road near Kabul's international airport

Image copyright Reuters Image caption Afghan and foreign security personnel were quick to arrive at the scene of the attack

Image copyright AFP Image caption This is the second attack on Kabul airport in days

An interior ministry spokesman said that the guards were protecting the entrance to the building, where counter-narcotics operations throughout Afghanistan are organised and executed.

Taliban spokesman Zabihulllah Mujahid told the Reuters news agency that "up to 15 invader soldiers were killed or wounded and many vehicles were damaged".

The attacks come against the backdrop of a hotly disputed election process.

The election commission is conducting an audit of votes cast during a presidential run-off, held on 14 June.

Ashraf Ghani won the run-off, according to preliminary results. His rival Abdullah Abdullah came top in the first round in April, but failed to secure 50% of the vote to avoid the run-off.

Both candidates accuse each other of electoral fraud.