Unknown gunmen attacked two US military patrols in Samara city, north of Baghdad, an official of the Multi-National Forces (MNF) said here on Friday. The official affirmed at a news conference that the gunmen opened fire on the US patrols on Al-Motasim road in Samara city, located in Tikrit constituency north of the Iraqi capital. The official said the US patrols counter-attacked prompting the gunmen to flee the scene, affirming that no human casualty was reported.