The Aligarh Muslim University (AMU) on Saturday was shut down indefinitely following violent clashes between two rival groups of students that left 12 of them injured. One group belonging to Bihar and eastern Uttar Pradesh (UP) and the other to western UP and some other parts, opened fire in the university campus late on Friday night. Around half a dozen students belonging to the two factions have been injured in incidents of firing and brick-batting between the rival groups, he said. However, police sources said around 12 were injured in the clash, of which six received pellet injuries. The trigger for the clashes was a scuffle between some students who had gone to the university examination controller on Thursday to point out some irregularities.