KABUL, Aug. 21 (Xinhuanet) -- Four US soldiers were killed Sunday and three others injured in an improvised explosive device (IED) attack in southern Afghanistan on Sunday, the US military said.

    The unit was conducting offensive operations in support of an ongoing mission to find and defeat insurgents in the Deh Chopan area of Zabul province when the attack occurred, said the US military in a news release.

    The unit's mission is part of a much larger operation to disrupt insurgents and to thereby provide a safe environment for upcoming September elections, it added.

    The three were injured while trying to pull their fellow soldiers to safety, said the release. A number of secondary explosions, caused by a fire started by the IED blast, injured the three.

    The three soldiers were evacuated to a nearby forward operating base for treatment of shrapnel wounds and are in stable condition.

    "These soldiers were operating and fighting alongside Afghan National Security Forces," Maj. Gen. Jason Kamiya, Combined Joint Task Force-76 Commanding General, was quoted as saying.

    "The enemy knows that he is at a race with time, a race that he will inevitably lose," Kamiya added.

    Taliban, who vowed to derail the historic parliamentary election slated on Sept. 18, has intensified attacks against Afghan government and US troops. Over 800 people, including US and Afghan troops, insurgents and civilians were killed in the violence. Enditem