China says it prosecuted 20 cases involving national security in Tibet last year, pointing to continuing low-level unrest in the Himalayan region.

Official newspapers Monday quoted Tibet's top judge as saying the cases dealt a "heavy blow" to those seeking the region's independence. No details were given about individual cases or the number of people being prosecuted.

This year will see further high-pressure tactics against separatists, including those operating within Tibet's Buddhist religious establishment, said the judge, Lodar, who like many Tibetans uses just one name.

Tibet and ethnically Tibetan parts of western China have been under heavy security since a wave of sometimes violent rioting and protests against Chinese rule in 2008. Communist troops occupied Tibet in 1950, although Beijing says it has been part of China for centuries.