A Taliban suicide bomber attacked a Nato convoy on the outskirts of Kabul today killing at least seven people and wounding more than 50.
The attack came just days before the presidential election that the group has vowed to disrupt.
Two Afghans working for the United Nations were among the dead in the attack, the UN office in Kabul said.
The bomber used a car to strike the convoy as it travelled along a road near a British military base in the eastern edge of the city.
Nato said "reports indicate" that Nato troops "were killed and wounded in the blast" but gave no details.
The Taliban claimed responsibility for the blast.
In Kabul, British troops guarded the site of the suicide attack as rescuers rushed the wounded to hospitals.
About a dozen private vehicles were destroyed near the road where the attack happened. People used their hands to dig through the rubble of damaged buildings. Families carried the wounded away from the scene.
US, Nato and Afghan security forces are on high alert this week because of Thursday's vote. President Hamid Karzai is favoured to win but faces a stiff challenge from former Foreign Minister Abdullah Abdullah. About three dozen candidates are in the race.
Meanwhile in eastern Afghanistan two US troops were killed and three were wounded when their vehicle struck a bomb.
Those deaths brought to 26 the number of US service members killed in Afghanistan this month.
Elsewhere, a suicide bomber struck the gates of an Afghan army base in the southern province of Uruzgan, killing three Afghan soldiers and two civilians.
And hours before the Kabul attack two mortar rounds struck near the presidential palace. No-one was wounded in the attack.
Despite the upsurge in violence, Nato announced its forces would stop offensive military operations on election day unless the missions were "deemed necessary to protect the population".
Attacks in Afghanistan have risen steadily the last three years. Yesterday President Barack Obama said US troops would help secure polling places so that the elections can go forward and Afghans can choose their own future.
He said peace in Afghanistan "will not be quick" and "will not be easy." He added that the United States still has a deep interest in the long-term outcome.
"This is not only a war worth fighting. This is fundamental to the defense of our people," he said.