"We believe that along with the legitimate interests in utilizing the water resources of the Mekong River for development, countries need to have a mutual responsibility in using the water source and resources fairly and sustainably, ensuring the balanced interests for all countries, for the prosperity and sustainable development of the region," Foreign Ministry spokeswoman Le Thi Thu Hang said Thursday.

She was responding to questions raised at a regular press meet about the impacts of China launching a trial run of the Jinghong dam from January 1 to 4.

"Vietnam always monitors, studies and evaluates activities regarding the water source of the Mekong River," Hang said.

The dam reduced the water’s output from 1,200-1,400 m3/s down to 800-1,000 m3/s during the first three days, before further reducing it to 504-800 m3/s on January 4. The water output was restored to normal levels later, said China's Ministry of Water Resources.

Thailand had previously warned that eight of its provinces along the river would experience water shortages due to the dam’s trial run, estimating water levels to fall by 40-110 cm.

Vietnam's Ministry of Agriculture and Rural Development on December 31 warned that the Jinghong dam's trial run would adversely affect salinity intrusion in the Mekong Delta.

Recent studies by the Mekong River Commission have shown that drought in the lower Mekong Basin has increased in frequency and severity in recent decades. Water levels in the river also reached critically low level in summer last year, said the commission in a press release in July last year.

Unseasonably low rainfall, weak water output from upstream areas caused by maintenance work at the Jinghong hydropower dam in China, and severe drought in several Southeast Asian countries, including Thailand, Laos and Myanmar last summer had led to massive declines in water levels and severely disrupted lives of millions who depend on the river for their livelihood.