U.S. Marines patrol the city of Kubaysah in western Iraq

U.S. troops have killed eight insurgents in western Iraq, as military officials dispute claims that militants have kidnapped two U.S. Marines.

About one thousand U.S. troops launched the offensive near the Syrian border, in the latest attempt to drive insurgents from the area. 

Residents said the operation appeared to be widening Sunday to several nearby towns.

Meanwhile, U.S. officials said they had no reason to believe an alleged statement from al Qaida in Iraq claiming to have kidnapped two Marines involved in the military offensive.

In a statement, U.S. officials said they were conducting checks to verify that all Marines were accounted for.

An Islamist web site carried the kidnapping claim, which demanded the release of female Sunni Muslim prisoners.

In Baghdad, militants freed the brother of Interior Minister Bayan Jabor, who was kidnapped one day earlier near the Sadr City district.

Some information for this report provided by Reuters, AFP and AP.