A student burned himself to death Saturday to protest a quota plan that reserves jobs for low-caste Hindus, police said. The incident set off riots in at least four cities.

The student's self-immolation took place in the Hindu holy city of Kurukshetra, 93 miles north of New Delhi, where the riots began.The violence quickly spread to New Delhi, authorities said, where angry students damaged 40 buses and blocked roads. The capital's 50,000 police were put on maximum alert.

The army was called out in Kurukshetra to bring the students under control after demonstrators torched the office and home of the district's top adminstrator, a police spokesman said.