At least 20 Indian soldiers are said to have been killed during an attack on a convoy by Maoist fighters in the state of Manipur.
The attack comes amidst increased tensions over the death of a local woman activist, killed by members of the paramilitary Assam Rifles. The government has accepted responsibility for the death of 55-year old Ruisoting and agreed to pay compensation to her family.
Prime Minister Narendra Modi said the attack on the troops is very "distressing".
"Today's mindless attack in Manipur is very distressing. I bow to each and every soldier who has sacrificed his life for the nation," Modi wrote on his Twitter account.
Manipur in India's north-east has seen battles between armed groups and the Indian military for decades. Locals accuse the government of exploiting the region's natural resources, forcibly displacing and neglecting the tribes who inhabit the area.