Separatist rebels from India's north-eastern state of Nagaland say Burma has launched a military offensive against their camps on its territory.
Burmese troops are believed to be targeting a faction of the National Socialist Council of Nagaland (NSCN), Indian military officials say.
The Burmese move follows a similar offensive against insurgents in Bhutan.
This is not the first time that Burma has attacked rebels fighting for a tribal homeland in north-east India.
But the BBC correspondent in the area says the offensive assumes significance because it comes so soon after the Bhutan operation.
Troops target rebel HQ
A spokesman for the NSCN faction led by SS Kaplang said that two of its camps had been overrun.
Burmese troops were closing in on the faction's headquarters in the Tenu Tekhap Joku valley in western Burma, the spokesman said.
But he added the rebels were confident of fighting back.
There have been no reports of casualties so far.
Indian military officials said they were closely watching the situation.
Last week, India said it might launch joint military operations with Burma, also known as Myanmar, against rebels based on Burmese soil.