A 5.4-magnitude earthquake jolted northwest China's Qinghai Province at 10:15 p.m. Tuesday, according to the China Earthquake Network Center.
The quake struck the Tanggula Range within the Haixi Prefecture of Qinghai, with the epicenter at 33.2 degrees north latitude and 92.0 degrees east longitude, the center said.
Earlier on Tuesday, the region had been struck by two other tremors with similar magnitude.
A 5.1-magnitude earthquake hit at 7:04 p.m. and a 5.5-magnitude one hit at 6:04 p.m..
Casualties and damages are not immediately available.
However, according to the center, the affected area is sparsely populated as it is on an altitude of about 5,000 meters above sea level.
The China Earthquake Administrative said in a late night press release it had beefed up the quake surveillance in the affected and neighboring areas following instructions of Vice Premier Hui Liangyu.
The administration would closely follow the development of the situation, organize experts to have more consultations and study the trend of the quake development, it said.
Emergency response work in the affected area would also be stepped up, it said.
Approximately the same area had been rocked by another moderate quake a day earlier.
The 5.0-magnitude tremor hit at 1:56 a.m. Monday, with the epicenter at 33.2 degrees north latitude and 92.2 degrees east longitude. No casualties were reported.
Also on Tuesday, a 5.2-magnitude quake rocked the northern Inner Mongolia Autonomous Region at 2:05 p.m..
The epicenter was located along the border between Oroqen Banner and Arong Banner at 49.0 degrees north latitude and 122.5 degrees east longitude, the network said.
The epicenter was inside a forest and there were no reports of casualties so far, said the Inner Mongolia regional earthquake bureau.
China has detected in southwestern Sichuan Province a total of 11,380 aftershocks of the May 12 8.0-magnitude earthquake, which has killed 69,146 people and led to the missing of 17,516 others.
In the 24 hours ending Tuesday noon, 186 aftershocks were monitored in the quake zone, according to the China Earthquake Administration.
One of the tremors measured between 5.0-5.9 and all the others measured at or below 3.9 magnitude, the administration said.
(Xinhua News Agency June 11, 2008)