In Saturday's other incidents, a Canadian soldier from the US-led foreign force was seriously wounded in a clash in the Shawali Kot district of Kandahar, Lieutenant Mark MacIntyre, Canadian spokesman, said.
Colonel Jim Yonts, US spokesman, said at least one Taliban fighter was killed in that clash and two were killed in the one in which the French officer died. The French Defence Ministry said he was a naval officer with special forces.
The wounded Canadian would be evacuated to a US military hospital at Landstuhl in Germany, the US spokesman said.
Saturday's bloodshed came as George Bush, the US president, was in neighbouring Pakistan discussing ways to improve co-operation in the US-led "war on terrorism".
Qari Mohammad Yousuf, Taliban spokesman, said the insurgents planted the bomb which killed the Afghans in Helmand province, neighbouring Kandahar, as part of a campaign to overthrow the US-backed government. He said nine people were killed.
The blast in Nadali district of Helmand killed Mohammad Ali Borak, a local official of the National Security Administration, said Asadullah Sherzad, head of the agency in the province.
"It was a remote-controlled bomb," Sherzad told Reuters, adding that an Afghan electrician who had been travelling in the same vehicle as Borak and his three bodyguards were also killed.
British soldiers are setting up
bases in violence-hit Helmand
The attack was the latest in a spate on insurgent violence to hit Helmand. On Friday, Taliban assailants killed the chief government official in Sangin district, hours after police killed eight insurgents and captured 10 in a two-hour battle.
The Canadian casualty was just the latest suffered by their 2300-strong contingent in Kandahar this week.
On Friday, five Canadian soldiers were hurt, one seriously, in a suspected suicide car bombing that followed a wave of such attacks in recent months that had killed dozens of people.
On Thursday, a Canadian soldier was killed and seven hurt when their vehicle overturned. Police said it was an accident and brought Canadian fatalities in Afghanistan to at least 10 since 2001.
The violence in Helmand comes as the British troops set up bases as part of an expanded Nato deployment intended to allow Washington to cut its troop numbers in Afghanistan.