UN Secretary-General Antonio Guterres "is profoundly saddened" by the devastating loss of life caused by the earthquake in China's Xizang Autonomous Region, his spokesperson said on Tuesday.

In a statement, the UN chief wished a speedy recovery to those injured and expressed his sincere condolences to the victims' families.

"The United Nations is closely monitoring the situation and stands ready to provide support if requested," Guterres said.

A total of 126 people have been confirmed dead and 188 others injured after a 6.8-magnitude earthquake jolted southwest China's Xizang Autonomous Region on Tuesday morning, toppling thousands of rural houses on the northern slope of the Himalayas.