US ambassador to China Gary Locke chatted with Buddhist monks, visited famous sites and mixed with locals on a rare trip to Tibet, photos released Tuesday showed.

The State Department announced that Locke was travelling in the Himalayan region from Tuesday to Friday last week.

It was the first time since September 2010 that Chinese authorities had granted a US ambassador access to tightly-controlled Tibet.

During the trip, Locke urged Chinese authorities to open the area up to tourists and diplomats and highlighted the importance of preserving Tibet's cultural heritage, the State Department said.

Security has been tightened and travel restrictions imposed in the Tibet Autonomous Region since deadly riots against Chinese rule erupted in March 2008 in the capital Lhasa and nearby areas.

Since 2009 China has been swept by a wave of self-immolations by Tibetans, with more than 100 setting themselves on fire and many dying in protests against Beijing.

Among the photos released by the US embassy on Tuesday, Locke could be seen walking up what appeared to be a steep stone pathway at a Buddhist monastery in the region known for its high elevation.

Other photos showed Locke, a former governor of the state of Washington and US commerce secretary, holding talks with Chen Quanguo, the Communist Party secretary of the Tibet Autonomous Region, visiting Lhasa's landmark Potala Palace and posing with Tibetan women and monks.