At least 37 members of Indian paramilitary Central Reserve Police Force were killed in Indian-administered Kashmir in one the deadliest attacks on government forces there, police said on Thursday, February 14.

The suicide bombing outside Srinagar claimed by Pakistan-based Jaish-e-Mohammed Islamist group is likely to ratchet up tensions between the two countries, with New Delhi long accusing Islamabad of supporting militants.

“The sacrifices of our brave security personnel shall not go in vain,” Indian Prime Minister Narendra Modi tweeted, calling the attack “despicable.”

Dozens killed in Indian Kashmir suicide bomb attack https://t.co/oDXCSrKoOU pic.twitter.com/oLfVZZEz20 — FRANCE 24 (@FRANCE24) February 14, 2019

The attack saw explosives packed inside a van rip through buses in a convoy of 78 vehicles carrying some 2,500 members of the CRPF.

Two blue buses carrying around 35 people each bore the brunt of the massive blast, heard miles away, around 12 miles (20 kilometers) from the city of Srinagar on the main highway to Jammu.

The Press Trust of India 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 identify them, PTI reported. The convoy was bringing the troopers back from leave to rejoin active service.

It was unclear whether the van containing the explosives was driven into the convoy or whether it was detonated when the buses were adjacent. Reports said there were 770 pounds (350 kilos) of explosives used.

A spokesman for Jaish-e-Mohammed Islamist group told a local news agency that the “suicide attack” was carried out by Aadil Ahmad, alias Waqas Commando, a known militant from the area.

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.

PM @narendramodi spoke to the National Security Advisor and took stock of the situation regarding the attack in Pulwama, Jammu and Kashmir. — PMO India (@PMOIndia) February 14, 2019

The U.S. ambassador to India, Kenneth Juster, tweeted that Washington “strongly condemns today’s terrorist attack in Jammu & Kashmir. We send our heartfelt condolences to the families of the victims.”

The attack surpasses one in 2016 that was the biggest in 14 years, claiming the lives of 19 soldiers in a brazen pre-dawn raid by militants on the Uri army camp.

India blamed militants in Pakistan for that attack, and responded with strikes across the heavily-militarised Line of Control, the de-facto border dividing the nuclear-armed nations.

The “surgical strikes” several miles (kilometers) inside Pakistan-controlled Kashmir remain a source of national pride for Modi’s government and were the subject of a rip-roaring recent Bollywood film.

Under Modi, not only terror attacks but also the death of Indian security forces has increased dramatically in Kashmir. The number of security persons killed in Kashmir – 47 in 2014, 39 in 2015, 82 in 2016, 80 in 2017 and 91 in 2018. pic.twitter.com/gw9J2unvbt — Ashok Swain (@ashoswai) February 14, 2019

India’s Foreign Ministry, in a statement late Thursday, blamed Pakistan.

“This heinous and despicable act has been perpetrated by Jaish-e-Mohammed, a Pakistan-based and supported terrorist organization proscribed by the United Nations and other countries,” the foreign office said. “India is firmly and resolutely committed to take all necessary measures to safeguard national security. We demand that Pakistan stop supporting terrorists and terror groups operating from their territory.”

Islamabad, however, rejected the suggestion that it was involved.

“We have always condemned acts of violence anywhere in the world,” the Pakistan Foreign Ministry said. “We strongly reject any insinuation by elements in the Indian media and government that seek to link the attack to Pakistan without investigations.”

India condemns in the strongest possible terms the cowardly terrorist attack on our brave security forces in #Pulwama, Jammu & Kashmir earlier today perpetrated by Pakistan based terrorist group Jaish-e-Mohammedhttps://t.co/qDRGM7CmYc pic.twitter.com/yObauXBnHS — Raveesh Kumar (@MEAIndia) February 14, 2019

Before Thursday’s violence, the biggest attack on Indian forces was in May 2002, when militants attacked an Indian army camp in Kaluchak in Jammu city, killing 34 people, including family members of soldiers.

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.

Last year was the deadliest in a decade, with rights monitors saying almost 600 people died, most of them civilians. Thousands more have been maimed in recent years by pellet-firing shotguns used by Indian forces.

Pakistan says it only provides diplomatic support to Kashmiris’ right to self-determination.

With reporting from AFP