KABUL (Reuters) - A member of the NATO-led force in Afghanistan and a civilian contractor have been killed in the latest "insider" attack by a member of the Afghan security forces, the coalition said on Sunday.

The attack, which took place in eastern Afghanistan on Saturday, came after the United States said joint operations with Afghan forces were returning to normal.

Joint operations were halted two weeks ago after a surge of attacks on the NATO-led International Security Assistance Force (ISAF) by its Afghan allies. At least 52 ISAF service members have been killed this year in "green-on-blue" attacks.

It was too early to say what impact the latest incident would have on plans to restore joint operations with Afghan troops to normal, a spokesman for ISAF said.

The attack took place in the Sayed Abad district of the Wardak province, according to local police sources, who said a gun battle broke out between coalition soldiers and Afghans when an Afghan National Army member opened fire on American troops.

Three members of the Afghan National Army were also killed in the fire fight, while three other U.S. citizens and one Afghan were wounded, police spokesman Wali Mohammad said on Sunday.

If the U.S. deaths are confirmed by Department of Defence, Saturday's insider killing would take U.S. civilian and military deaths in Afghanistan to over 2,000.

"We appreciate the sacrifice of our fallen heroes, every death is tragic and important - none more than any other," ISAF said in a statement after Saturday's attack.

(Reporting by Jessica Donati; additional reporting by Mirwais Harooni in Kabul and Mustafa Andalib in Ghazni; Editing by Robert Birsel and Daniel Magnowski)

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