Casualties of an earthquake in southwest China's Yunnan province has reached approximately 600 by Wednesday noon, according to local sources.

The quake measuring 5.6 on the Richter scale jolted Ludian county in Zhaotong city of Yunnan Tuesday night.

According to Deng Xianpei, mayor of Zhaotong city, the quake has killed three locals, including two in Ludian county and one in Zhaoyang district of Zhaotong city. A total of 594 people were injured, and 142 of them seriously.

It was the third major quake that hit the Ludian county within a year. Two other quakes measuring 5.1 and 5.0 on the Richter scales struck the county on Nov. 15 and 26, 2003. Four people were killed and 120 were injured in the two previous quakes.

With a population of 370,000, Ludian county, located in the east of Yunnan province, is among China's abject counties.