At least four Afghan civilians and a British soldier have been killed in a suicide bomb attack on a Nato convoy in the capital, Kabul, officials say.
Suicide attacks are quite rare in Kabul
At least three UK soldiers and four civilians were hurt in the blast on the Kabul-Jalalabad road.
Separately, a Canadian soldier has been killed and several others wounded in a so-called "friendly fire" incident.
The deaths come amid a major offensive against the Taleban. The UK lost 14 servicemen in an air crash on Saturday.
Initial reports from Afghan police said two British soldiers had been killed in the Kabul bombing, but in a later statement the UK Ministry of Defence (MoD) said one soldier had died and another was very seriously injured.
An Afghan interior ministry spokesman told Reuters news agency the suicide bomber had rammed his car into the Nato convoy.
The friendly fire death happened at dawn as Nato troops battled Taleban insurgents in the Panjwayi district, west of Kandahar.
The soldiers called in air support and two Nato aircraft responded, but fired cannon at their own soldiers during a strafing run. Several soldiers were wounded.
About 2,000 Nato and Afghan soldiers are involved in Operation Medusa in southern Afghanistan.
It is the biggest military operation in southern Afghanistan since the Nato-led International Security Assistance Force (Isaf) took over the area from a US-led coalition at the end of July.
It is concentrated on the Panjwayi area, about 35km (20 miles) west of Kandahar city, which has seen months of fighting.
More than 200 Taleban fighters and four Canadian soldiers with the Nato forces were killed in the operation over the weekend, Nato said.
An Afghan defence ministry spokesman put the suspected Taleban losses at 89, and said a number of civilians had also died.
Nato spokesman Mark Laity told the BBC that Nato forces were currently undergoing a period of "intense combat", particularly in the south of the country.
But he said forces were "not fighting for fighting's sake".
"Our ultimate goal is still the same as when we came - which is to secure more stability in order that development and governance can take place."
On Monday, police in southern Afghanistan said they had beaten off an attack by Taleban rebels on local government headquarters in the town of Garmser in Helmand province.
The town's police chief said 16 Taleban fighters had died in the attack. Three policeman were also killed during several hours of fighting.
In a separate incident, two police including a senior officer were killed in an ambush near Kabul, the Afghan officials said.
The attack took place late on Sunday in Parwan province about 30km (18 miles) north of the capital.