PARIS — France suffered its biggest loss of life on the battlefield in 25 years when 10 paratroopers were killed in an ambush in Afghanistan.

Another 21 soldiers were injured and 13 Taliban fighters killed during the battle in the Sarobi district, 30 miles east of Kabul, which began on Monday afternoon.

The scale of the casualties prompted President Sarkozy of France to fly to Afghanistan immediately to visit the wounded and speak to military commanders.

“In its fight against terrorism, France has been dealt a harsh blow,” Mr. Sarkozy said as he prepared to board a plane to Kabul from Paris.

“I acknowledge with respect and emotion the courage of these men, who fulfilled their duty to the point of the supreme sacrifice. My determination is intact. France is determined to pursue the struggle against terrorism, for democracy, and freedom.”

The French 8th Infantry Parachute Regiment was on a joint reconnaissance mission with the Afghan army when they were ambushed. After an initial three-hour gun battle, shooting continued sporadically overnight.

About 100 Taliban fighters were involved. A spokesman for the group later claimed that they had destroyed five armored personnel carriers using landmines in an area known as a militant stronghold.

Rocket launchers and machine guns were also used again the French, who responded by calling in air strikes by NATO warplanes.

At one point in the two-day battle four of the French soldiers, all part of a NATO force, are believed to have been captured before being killed.

The latest deaths will mean France has lost 24 service personnel during Operation Enduring Freedom, the campaign to rid Afghanistan of terrorist insurgents.

There have been 116 British fatalities, 574 American, and 89 Canadian among 40 countries operating in the International Security Assistance Force since the American-led invasion in 2001. The French losses underscore Mr. Sarkozy’s effort to reverse the perception that his country is not doing enough to assist its NATO allies.

Paris withdrew its special forces soldiers previously deployed in Afghanistan after taking high casualties. Some of their dead were reported to have been skinned alive after being captured.

France has more than 1,500 personnel in the country and has promised 700 more later this year. The latest attack was the deadliest against international troops in Afghanistan since June 2005, when 16 Americans were killed in Kunar province when their helicopter was shot down.

The battle yesterday was the bloodiest for the French army since a 1983 bombing in Lebanon in which 58 French paratroopers were killed.