Indian officials say China is assisting rebel groups that have stepped up attacks on its border with Myanmar in recent months, opening another front in the conflict between two nations already engaged in a deadly standoff in the Himalayas.

Armed groups in Myanmar — including the United Wa State Army and the Arakan Army, which was designated a terrorist organization this year — are acting as Beijing’s proxies by supplying weapons and providing hideouts to insurgent groups in India’s northeastern states, according to Indian officials with knowledge of the situation, who asked not to be identified due to rules for speaking with the media.

The officials said multiple security agencies warned Prime Minister Narendra Modi’s government that at least four of India’s most wanted insurgent leaders were in the southern Chinese city of Kunming to train and source weapons as recently as mid-October. The group — including three ethnic Naga rebels fighting for a separate homeland in an area straddling the India-Myanmar border — met with acting and retired Chinese military officials as well as other middlemen who make up an informal network, the Indian officials said.