Meanwhile, Isaf said another Nato member was killed "as a result of an individual wearing an Afghan National Army uniform turning his weapon against Isaf members" on Monday.
The incident means 47 Isaf members have died this year at the hands of Afghan military or police personnel, or by insurgents posing as them.
At least 52 Isaf service members have been killed this year in so-called "green-on-blue" attacks.
Colonel Vician, the military spokesman, said that the tempo of the fighting had slowed in Marja by Tuesday, although two more ISAF service members, neither American, were killed on Tuesday, one by a homemade bomb, the other by small arms fire.
"An individual wearing ANA (Afghan National Army) uniform turned his weapon against the Isaf service members," an Isaf statement said.
Last year about 10 times as many Afghan security force members as Isaf troops were killed.
After the Taliban fled those bombs, the first soldiers to patrol the ruined streets of Kabul were members of ISAF, the International Security Assistance Force established by the U.N. to safeguard the capital.
Last month, after US servicemen accidentally burned Korans, 30 Afghans were killed in demonstrations, six Isaf soldiers were killed by members of the Afghan security forces who turned on them in apparent revenge, and two US military advisers were shot dead.
The official said the operation was led by about 100 Afghan security force members accompanied by 17 ISAF military advisers.
First, because several of its member states are foot-dragging, as the composition of ISAF's forces shows.
