BAGHDAD (Reuters) - Multiple rockets fell on Saturday morning inside Iraq's Taji military base that houses U.S.-led coalition troops, for the second time in a week, security sources told Reuters.

An Iraqi colonel inside the base told Reuters he heard at least 10 rockets hit the base and said he could now hear sirens blaring. It was not immediately clear if there had been any casualties and no group has claimed responsibility.

The Iraqi army found an abandoned truck with a rocket launcher and some unused Katyusha rockets on its back in the nearby area of Umm al-Izam, security sources said.

A similar rocket attack on Wednesday on Taji, 20 kilometres (12 miles) north of Baghdad, killed two U.S. troops and a British soldier, prompting Washington to launch retaliatory air strikes on Thursday that killed six Iraqis.

The United States blamed the Iran-backed Kataib Hezbollah Iraqi militia for the attack on Wednesday and said its air strikes targeted the group. But the official Iraqi casualty figures showed three Iraqi soldiers, two policemen, one civilian and no militiamen had been killed.

Iraq condemned the U.S. air strikes on Friday, saying they were a violation of sovereignty and targeted aggression against its regular armed forces.

Longstanding antagonism between the United States and Iran has mostly played out on Iraqi soil in recent months.