A suicide bombing claimed by the Taliban killed three Czech soldiers on patrol in eastern Afghanistan on Sunday, the deadliest assault on Nato troops for many months.
"Three Resolute Support service members were killed by a suicide bomber during a combined, dismounted patrol with Afghan forces in eastern Afghanistan," Nato's Resolute Support mission said in a statement.
In Prague, the military said the dead soldiers were Czech.
A US member of the patrol and two Afghan soldiers were wounded, Nato added.
The attack by a lone bomber on foot happened at 6am in the city of Charikar in Parwan province 60 kilometres (37 miles) north of Kabul, said provincial governor's spokesman Wahida Shahkar.
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The Taliban in a statement claimed responsibility, saying they killed or wounded eight American soldiers in a "tactical explosion".
The Czech army said in a statement that three of its soldiers - a staff sergeant and two corporals - were killed in the explosion.
"The tragic death of our three soldiers has struck me deeply, and I wish to express my deepest condolences to their families," said Defence Minister Lubomir Metnar.
The Nato force largely ended its combat mission in Afghanistan in 2014 and pulled out the bulk of its troops. A 16,000-strong residual force remains for training and counter-terrorism operations.
Of these, the US accounts for 13,000 soldiers, about 2,000 of whom are assigned to anti-terror combat missions.
Last month a US soldier was killed and two others wounded in an "apparent insider attack" in southern Afghanistan.
Casualties among the Nato force have fallen dramatically since most were withdrawn from combat.
But the Taliban and the Islamic State of Iraq and the Levant (Isil) have recently stepped up their attacks against government and civilian targets.
On Friday two suicide bombers dressed as women struck a Shiite mosque in Gardez, the capital of Paktia province, while it was crowded with worshippers for weekly prayers. Thirty-five were killed and more than 90 wounded.
The burqa-clad attackers shot at the mosque's security guards before opening fire on worshippers and then detonating their explosives.