At least 21 Chinese grounded boats have been rescued on the Mekong River, a cross-border river flowing out of China from southwest China's Yunnan Province, the marine affairs bureau in Yunnan said on Tuesday.

The bureau's subsidiary in Xishuangbanna Dai Autonomous Prefecture, which borders Laos and Myanmar, has stopped issuing pass permits to vessels and repeatedly sent warnings to foreign vessels, telling them of the danger.

"The river is at its lowest level in 50 years. The boats grounded in the river sections in Laos and Myanmar have been pulled to relatively safer waters on the river or to docks in Thailand. But the vessels are not completely out of danger," said Liu Rongming, deputy chief of the Xishuangbanna bureau.

He said Chinese rescuers have sent relief goods and money to the crews.

The river's flow is only half the normal level, as a rare, large-scale drought -- the worst in 50 years -- hits southwest China, according to the bureau.

The river, called Lancang River, flowed at 240-260 cubic meters per second Monday, compared with 400-500 cubic meters per second in normal years.

The drought started in July last year has brought drinking water shortages to 4.9 million residents and 3.34 million livestock, according to the provincial headquarters of drought relief.

The provincial headquarters said 187 forest fires have been reportedly extinguished in the province since November last year, which is 56 percent more than the number in the same period of the previous year.

A fire burning for two days in a forest near Kunming, the provincial capital, was basically brought under control on Tuesday, according to the Forest Fire Control Headquarters in Xishan District, Kunming.

The headquarters said 15 hectares of forest was destroyed, mainly pine and eucalypt trees. More than 800 fire fighters were dispatched to fight the fire.

The provincial drought relief headquarters said Yunnan has newly recruited 16,171 forest wardens to bring the total number to 70,000, in order to closely monitor forest fires.

The meteorological station in Yunnan's neighboring region, Guangxi Zhuang Autonomous Region, said the rare drought had also affected Guangxi and Guizhou provinces. Some of these provinces' regions have not seen rain since August last year.

"Such an extreme drought has not been seen for 50 years," said Tan Zhinian, chief weatherman at the station.

He said scientists with the station has noticed an El Nino affecting southwest China, which is likely related to the extreme weather.

The station has also noticed that the average temperature in Guangxi has risen 0.13 degree Celsius every ten years. The temperature rise has been faster in winter, when it climbed 0.21 degree Celsius every ten years, he said.