At least 44 Indian paramilitary soldiers were killed on Thursday in Indian-administered Kashmir in the deadliest attack on government forces there since 2002.
The suicide bombing outside Srinagar claimed by an Islamist group is likely to ratchet up tensions between nuclear-armed arch rivals India and Pakistan, with New Delhi long accusing Islamabad of supporting militants.
“The sacrifices of our brave security personnel shall not go in vain,” Indian Prime Minister Prime Minister Narendra Modi tweeted, calling the attack “despicable”.
The attack saw explosives packed inside a van rip through buses in a convoy of 78 vehicles carrying some 2,500 members of the paramilitary Central Reserve Police Force (CRPF).
Two blue buses carrying around 35 people each bore the brunt of the massive blast, heard miles away, around 20 kilometres (12 miles) from the city of Srinagar on the main highway to Jammu.
The Press Trust of India (PTI) news agency reported that at least 39 people were dead, while other press reports said the number could exceed 40.
Some of the bodies were so badly blown up that officials feel it may take some time to identity them, PTI reported. The convoy was bringing the troopers back from leave to rejoin active service.
Local media reports said the Pakistan-based Jaish-e-Mohammed Islamist group claimed responsibility.
After the attack, hundreds of government forces cordoned around 15 villages in the district the bomber came from and started searching house-to-house, a police officer and witnesses said.
The last major car bombing, which killed 40 people including three suicide attackers, was also carried out by Jaish-e-Mohammed, in 2001. The target was the local parliament building in Srinagar.
Kashmir has been divided between India and Pakistan since independence. Rebels have been fighting for an independent Kashmir, or a merger with Pakistan, for 30 years.
New Delhi accuses Pakistan of fuelling the insurgency that has also left tens of thousands of civilians dead and which has become increasingly bitter in recent years.