MOSUL, Iraq, Oct 19 (Reuters) - Six suicide bombers in vehicles targeted Iraqi and U.S. security forces in the city of Mosul on Thursday, a U.S. general said. The attacks, including one involving a fuel truck that killed at least 11 people, were aimed at three Iraqi police stations and two U.S. patrols in the city which is a flashpoint of insurgent activity north of Baghdad. Major General William Caldwell also said there were four to six indirect fire attacks, a term the military normally uses for mortar fire. Police in Mosul said earlier 20 people were killed in the violence. Speaking at a news conference in Baghdad, Caldwell said he had no information on the number of casualties.