Officials say 10 French soldiers were killed and 21 wounded Tuesday when they were ambushed by about 100 insurgents in the Surobi district, 50 kilometres east of the Afghan capital.
It was reportedly the biggest single loss of life among international forces in combat in Afghanistan in three years.
Military officials say the soldiers, members of a parachute regiment, were attacked while on a reconnaissance mission in the area, a known militant stronghold.
An Afghan official said four of the soldiers were killed after having been captured by the insurgents.
Qazi Suliman, the district chief in Surobi, said the ambush sparked a three-hour gunbattle in which 13 insurgents also died.
NATO said it sent reinforcements and a “large number” of the 100 attackers died.
“In its fight against terrorism, France has just been struck severely,” French President Nicolas Sarkozy said in a statement.
“My determination remains intact,” he added. “France is resolved to pursue the fight against terrorism, for democracy and liberty. The cause is just, it is the honour of France and its armies to defend it.”
Mr. Sarkozy confirmed that 10 soldiers from the 8th infantry parachute regiment had been killed and 21 wounded.
One Western official described the attacks on the French as “complex.”
It is the deadliest attack against international troops in Afghanistan since June 2005, when 16 American troops were killed in Kunar province when their helicopter was shot down by a rocket-propelled grenade.
In July of this year, nine U.S. troops died when insurgents attacked a base on the Kunar-Nuristan border in eastern Afghanistan.
France will have some 2,600 troops in Afghanistan by the end of this month, after Sarkozy pledged in April to send 700 more troops to eastern Afghanistan. Mr. Sarkozy said he plans to travel to Afghanistan to reassure French troops and that “France is at their side.”
In a separate co-ordinated attack Tuesday, a team of suicide bombers tried unsuccessfully to storm a U.S. military base near the Afghanistan-Pakistan border.
Officials said the insurgents failed to gain entry to Camp Salerno in Khost after launching waves of attacks just before midnight Monday night, said Arsallah Jamal, the city’s governor.
A suicide bombing outside the same base on Monday killed 10 civilians and wounded 13 others.
Ground forces, fighter aircraft and helicopters chased the retreating insurgents. NATO said its forces identified the attackers about 1,000 metres outside of the base perimeter and launched helicopter gunships.
Gen. Mohammad Zahir Azimi, an Afghan Defence Ministry spokesman, said Afghan soldiers, aided by U.S. troops, chased and surrounded a group of insurgents, and that six militants blew themselves up when cornered. Seven others died in those explosions and a rolling gun battle, he said.
“(The Afghan National Army) is saying that any time we get close to them, they detonate themselves,” Mr. Jamal said.
NATO offered a slightly different account, saying three suicide bombers detonated their vests and three more were shot dead. NATO said seven attackers in total were killed.
At least 13 insurgents and two Afghan civilians died, officials said.
The Taliban appeared to confirm the account. Zabiullah Mujahid, a Taliban spokesman, said 15 insurgents had been dispatched for the attack on Salerno. Seven blew themselves up and eight returned to a Taliban safehouse, he said.
Mr. Jamal said the bodies of at least two dead militants were outside the checkpoint leading to the base’s airport. Both wearing vests packed with explosives, Jamal said.
Militants have long targeted U.S. bases with suicide bombers, but co-ordinated attacks on such a major base are rare.
On Monday, the top U.S. general in the region, Maj. Gen. Jeffrey J. Schloesser, issued a rare public warning that militants planned to attack civilian, military and government targets during the celebration of Independence Day on Monday.
More than 3,400 people â€” mostly militants â€” have been killed in insurgency-related violence this year, according to an Associated Press count based on figures from Western and Afghan officials.