Beijing approved the project in December on the river -- known as Yarlung Tsangpo in Tibet and Brahmaputra in India -- linking it to the country's carbon neutrality targets and economic goals in the Tibet region.

"The electricity generated will be primarily transmitted to other regions for consumption, while also meeting local power needs in Tibet," state news agency Xinhua reported after the groundbreaking ceremony in southeastern Tibet's Nyingchi.

Once built, the dam could dwarf the record-breaking Three Gorges Dam on the Yangtze River in central China -- and have a potentially serious impact on millions of people downstream in India and Bangladesh.

The project will entail constructing five hydropower stations, with the total investment estimated to be around 1.2 trillion yuan ($167.1 billion), Xinhua said.

India said in January it had raised concerns with China about the project in Tibet, saying it will "monitor and take necessary measures to protect our interests".

China "has been urged to ensure that the interests of the downstream states of the Brahmaputra are not harmed by activities in upstream areas", India's foreign ministry said then.

In December, Beijing's foreign ministry said that the project would not have any "negative impact" downstream, adding that China "will also maintain communication with countries at the lower reaches" of the river.

Besides downstream concerns, environmentalists have also warned about the irreversible impact of such mega projects in the ecologically sensitive Tibetan plateau.

Both India and China, neighbours and rival Asian powers, share thousands of kilometres of disputed borders, where tens of thousands of soldiers are posted on either side.