(MENAFN- Khaleej Times) The international security assistance force said the casualties occurred on monday when the unit came into contact with enemy forces.

five us servicemen were killed in southern afghanistan in a friendly-fire air strike during a security operation afghan police said on tuesday days before a run-off round in the country’s presidential election.

the international security assistance force (isaf) said the casualties occurred on monday when the unit came into contact with enemy forces. it did not give the nationality of the dead soldiers.

friendly fire incidents have been rare in afghanistan in recent years though five afghan soldiers were killed in a nato air strike in the eastern province of logar in march.

local police chief ghulam sakhi roghlewanai said of the incident in zabul province’s arghandab district: “the five killed were american soldiers who just returned from an operation when they were hit.

“isaf troops were returning to their bases after an operation when they were ambushed by the insurgents. the air strike mistakenly hit their own forces and killed the soldiers.”

a taleban spokesman qari yousuf ahmadi said insurgents had been attacking the foreign forces when the helicopters intervened and accidentally killed their own troops.

an isaf statement said an investigation was under way into “the possibility that fratricide may have been involved”.

mohsin khan spokesman for the afghan army’s 205 division which is deployed in zabul also said it was a friendly fire error.

“our forces were jointly engaged in fighting with militants and foreign forces called in air support and they mistakenly bombed friendly positions” khan said.

“i can confirm isaf suffered casualties. we also lost one soldier and one was wounded.”

an isaf spokesman declined to comment on reports that “friendly fire” was the cause of the deaths.

the us-led force is winding down operations in afghanistan after more than a decade of fighting taleban insurgents and the number of soldiers out on patrol has fallen rapidly in the last year.

the deaths were the worst single incident for the nato force since five british soldiers were killed in a helicopter crash on april 26.

security is being ramped up in afghanistan ahead of saturday’s run-off vote to replace president hamid karzai.

the poll pits abdullah abdullah a former leader of the opposition to the taleban against former finance minister ashraf ghani.

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