UNITED NATIONS -- The UN humanitarian office is monitoring developments after multiple earthquakes struck a mountainous region in southwest China, and stands ready to assist the Chinese government, UN spokesman Martin Nesirky told reporters here Friday.

Nesirky made the statement at a daily news briefing here, referring to the UN Office for the Coordination of Humanitarian Affairs (OCHA).

Sixty-seven people have been confirmed dead and 731 others injured after multiple earthquakes struck a mountainous region in southwest China on Friday, local authorities said.

Rescuers in Yunnan Province in southwest China said on Friday night they had reached 90 percent of the six quake-hit counties under Zhaotong, where a total of 740,000 people had been affected by the quakes.

The disaster has so far incurred 3.5 billion yuan ($551 million) in direct economic losses, Yunnan's civil affairs department said.

Two quakes measuring 5.7 and 5.6 on the Richter scale hit respectively a border area near Yiliang in Yunnan and Weining county in Guizhou Province at 11:19 am and 12:16 pm (local time) on Friday.