BAGHDAD, July 5 (Reuters) - At least three rockets landed on Monday on the Ain al-Asad air base, which hosts U.S. and other international forces in western Iraq, but caused no casualties, a coalition spokesman said. U.S. Army Colonel Wayne Marotto, spokesman for the U.S.-led international military coalition, tweeted that initial reports suggested the attack took place at 2:45 p.m.. He said the damage was being assessed. The United States accuses Iran-backed militia groups of launching regular rocket attacks against its troops in Iraq. There was no immediate claim of responsibility for Monday"s attack.