Indian police say eight soldiers have been ambushed and killed by rebels in the north-eastern state of Nagaland.
Reports said the attackers opened fire on Sunday when troops stopped to fetch water from a stream. The soldiers shot back, killing one of the gunmen.
Violence in the region has escalated since the government broke off a ceasefire last month with the rebels.
The rebels have been demanding an independent homeland for India's two million Naga tribespeople.
Police said six other soldiers were injured in Sunday's attack, and four were missing.
It was the second attack by rebels on Indian soldiers in recent weeks.
Last month, the separatists claimed responsibility for the death of three soldiers in the neighbouring state of Arunachal Pradesh.
The Naga mainly live in the north-eastern states of Nagaland, Manipur, Assam and Arunachal Pradesh.
The 58-year-old insurgency has been contained by a slew of ceasefires.
But chances of a settlement appear dim after 15 years of negotiations because the rebel factions cannot agree on the territorial limits of a future Naga homeland or state.
India's government says it cannot redraw state borders to allow all the Nagas to live together in one state.