A dozen people were arrested at the University of California at Irvine on Monday evening for disrupting a lecture by the Israeli ambassador to the United States, Michael Oren, according to a blog run by The Orange County Register, which also has photographs and video of the event. Mr. Oren was interrupted repeatedly by shouts from protesters irate over Israel’s treatment of Palestinians and by the university’s decision to play host to the talk. Mr. Oren was also occasionally interrupted by applause. The campus’s Muslim Student Union had early condemned Mr. Oren’s scheduled appearance. The university’s chancellor, Michael V. Drake, told the audience he was embarrassed by the disruptions. An Irvine spokesman told the Associated Press that those arrested were students at his campus as well as at UC-Riverside. All were cited and released.