Police in China's Tibet region have arrested 59 people suspected of "spreading rumours" in the nine months since Tibetans staged violent protests against Chinese rule in the regional capital of Lhasa, state media said on Friday.

After the protests and rioting in Lhasa in March, "some people started making up stories and spreading rumours, posing a threat to the security of the region and its people," the China Daily newspaper quoted Xin Yuanming, the city's deputy police chief, as saying.

A total of 59 people were arrested on suspicion of "spreading rumours that caused a security threat to the region," the newspaper quoted Xin as saying.

Virtual martial law was imposed in some areas of Tibet after pro-independence demonstrations and unrest began in Lhasa in early March.

The government said 19 people were killed in rioting from March 14 in Lhasa but the Tibetan government-in-exile said about 140 people were killed, most of them Tibetans shot by Chinese police.

Police detained thousands of Tibetans after independence protests and riots erupted in dozens of other Tibetan areas of China.

Courts have already sentenced many Tibetans convicted of taking part in the rioting earlier this year.

Last month, a court in the south-western city of Chengdu, Sichuan province, also sentenced an online activist to three years in prison after convicting him of subversion for supporting the Tibetan protestors.