At least 20 soldiers have been killed and 15 injured in an attack on a troop convoy in north-east India, police say.
The ambush occurred in the state of Manipur as the convoy made its way to Imphal, the state capital.
The region's deadliest in years, the attack is thought to be a retaliation for the death of a woman who soldiers are accused of killing on Monday.
Authorities in Manipur have struggled for years with an insurgency involving several militant groups.
Thursday's attack took place at 07:00 local time (01:30 GMT) in the state's Chandel district, close to the border with Myanmar.
Police said rebels used rocket-propelled grenades and assault rifles to target the soldiers.
No group immediately claimed responsibility for the attack, the worst in the area in more than a decade.
The attack came a day after shops and businesses in the state closed in protest over the alleged killing of a woman by soldiers.
Manipur has been relatively peaceful in recent years and the attack took authorities by surprise, said the BBC's Sanjoy Majumder from Delhi.
Along with other north-east Indian states, Manipur is poorly developed and has long complained of neglect by the federal government, fuelling unrest, our correspondent adds.
In April, insurgents opened fire at two trucks carrying Indian paramilitary soldiers in neighbouring Nagaland state, killing eight of them.
Indian security forces have for more than half a decade had sweeping shoot-to-kill powers in so-called "disturbed areas" under the Armed Forces Special Powers Act (AFSPA).
The controversial act was first enforced in Manipur in 1958 and later introduced in other insurgency-ridden north-eastern states.
The law has been blamed for "fake encounter" killings and campaigners say it is often misused. It was withdrawn in Tripura at the end of May.