Chengdu, China covered in a heavy haze (file photo)

Authorities in a major city in southwestern China have clamped down on a Tibetan neighborhood where there have been unconfirmed reports of protests this week.

Witnesses in Chengdu say security forces have locked down the neighborhood in the capital of Sichuan province near the Wuhou Temple and the Southwest University of Nationalities.

There were unconfirmed reports of a protest in the neighborhood earlier this week and of a Tibetan stabbing a Han Chinese man.

Police told a VOA correspondent in Chengdu that the situation is normal and that the rumors of Tibetans planning bomb attacks are false. But the correspondent says there is a heavy police presence near the Tibetan neighborhood and vehicles are not allowed through. Han Chinese taxi drivers told the correspondent they are refusing to take Tibetan passengers because they fear for their safety.

The United States and six other countries, France, Germany, Pakistan, Singapore, South Korea and Thailand maintain consulates in the city. But a State Department spokesman Thursday declined to say if U.S. diplomats are able to confirm reports of protests in Sichuan province and other Tibetan areas.

Chinese authorities have admitted firing on Tibetan protesters in Sichuan's Ngaba prefecture, but denied killing anyone. The Indian-based Tibetan government-in-exile says 19 people were shot and killed by police during the protests.

Rights group have released photographs of several bodies with bullet wounds that they allege were caused by police gunfire.

The Foreign Correspondents Club of China has reported official interference with journalists working in Chengdu, and authorities have tried to prevent foreigner reporters from traveling to other areas of the province where there have been demonstrations.

A Time Magazine correspondent earlier this week reporting seeing about 150 military vehicles traveling on the road to the Tibetan city of Lithang in Sichuan.