An attack on a police station in the troubled northwestern region of Xinjiang left four people dead and one person critically injured, official media reported.
Several "thugs" invaded a police station in Hotan, near the border with Pakistan, took hostages and set fire to the place, the state-run Xinhua news agency reported.
It said four people, including a police officer, were killed in the attack.
Xinjiang, where many Muslim Uyghurs chafe under Chinese rule, is no stranger to ethnic conflict. Deadly riots in the regional capital of Urumqi left at least 200 dead in July 2009.
Officers who answered the phone at a number of police stations in the region declined to give details of the attack, however.
"Sorry, but we can't talk to you," said one officer. "If I spoke to you, I'd lose my job."
"As to whether this had an ethnic angle, there will be an announcement from the spokesperson in due course," he added.
'Nothing out of the ordinary'
However, local residents said there had been chaotic scenes at the town's central bazaar area on Monday.
"I'm not sure about the attack on the police station," said a Hotan resident surnamed He. "There were clashes in the bazaar, but I don't know the details because I was at work."
He said rioting was fairly common in the region.
"I am from around here ... and these sorts of incidents are nothing out of the ordinary," he added. "I'm talking about riots, not attacks on police stations ... We have got used to them and are not surprised by them."
A second resident surnamed Wang said he too had heard nothing about the reported attack on the police station.
"It seems as if the main incident took place over at the bazaar," Wang said.
An overseas Uyghur activist group said Monday’s violence stemmed from a land protest earlier in the day that ended in clashes between demonstrators and police.
Xinhua said the situation was now "under control," adding that back-up police forces had rushed to the scene of the attack and shot dead “several people” in the process of rescuing the hostages.
Protesting land seizure
According to Dilxat Raxit, spokesman for the Munich-based World Uyghur Congress, clashes were sparked after a large group of Uyghurs tried to stage a protest in Hotan.
He said more than 100 Uyghur protesters were demonstrating against the seizure of their land and to demand information about relatives who had "disappeared" in a region-wide security crackdown since the Urumqi riots of 2009.
Uyghurs in the Silk Road city of Hotan have complained of intensive political campaigns aimed at their religious lives, including campaigns against the wearing of beards or headscarves, and obstacles to fasting during the holy month of Ramadan.
Uyghurs say they have long suffered ethnic discrimination, oppressive religious controls, and continued poverty and joblessness despite China's ambitious plans to develop its vast northwestern frontier.
Chinese authorities blame Uyghur separatists for a series of deadly attacks in recent years and accuse one group in particular of maintaining links to the Al-Qaeda terrorist network.
Reported by Ding Xiao for RFA's Mandarin service, and by Bi Zimo and Wei Ling for the Cantonese service. Translated and written in English by Luisetta Mudie.