A pipeline pumping natural gas from Myanmar to energy-hungry China has gone fully operational, state-run Chinese media said on Monday.

The project, stretching more than 2,500 kilometres (1,600 miles) from western Myanmar to southwest China, will help the world's second-largest economy feed its growing energy needs.

It comes as close political ties between the two nations have weakened, after Myanmar's quasi-civilian regime took office in 2011 and brought in sweeping reforms that have led to the scrapping of most Western sanctions.

The pipeline, first launched in July after three years of construction, "has gone into full operation on Sunday", the Global Times reported.

It runs from Kyaukpyu on the west coast of Myanmar and will deliver gas to Myanmar and China's energy-deprived southwest, including Yunnan, Guizhou, Chongqing and Guangxi.

But critics say the project saw land confiscated from local residents and carries environmental risks.

The pipeline also passes through the Chinese border town of Ruili, where fighting erupted earlier this year between Myanmar government forces and the rebel Kachin Independence Army.

The added delivery of 12 billion cubic metres (420 billion cubic feet) a year will cut gas prices and reduce coal use, the Global Times said, while limits on industrial gas consumption will be raised.

The pipeline will help China diversify its energy imports, it quoted Lin Boqiang, a professor with the China Centre for Energy Economics Research at Xiamen University, as saying.

"Currently, China's piped gas is mainly imported from areas around the Malacca Strait. Now, we have one more pipeline from the land instead of the seabed, which will decrease dangerous factors," Lin said.