At least 18 Indian paramilitary officers were killed in a suicide bombing on a vehicle convoy in Indian-administered Kashmir.
The police told the BBC that an explosives-fueled car rammed a bus that took the officers to Srinagar, the capital of India-administered Kashmir.
Pakistan-based Islamist group Jaish-e-Mohammad said it carried out the bombing.
It is the deadliest attack on security forces in Kashmir for two decades.
The explosion took place on the heavily guarded Srinagar Jammu Highway, about 20 km from the city of Srinagar.
"It is not yet clear how many vehicles were in the convoy that was on the way from Jammu to Srinagar, a car overtook the convoy and rammed a bus into a bus with 44 employees," a senior police officer told Riyaz Masroor of BBC Urdu.
He said the death toll could rise as dozens are "critically injured".
Two former prime ministers, Omar Abdullah and Mehbooba Mufti, have tweeted about the attack.
AFP said that Jaish-e-Mohammad had sent a statement to the local media that he was behind the attack.
At least 17 Indian soldiers were killed when fighters stormed a base in Uri in 2016. This was the deadliest attack on security forces in Kashmir in two decades and came amid violent protests against Indian rule. Delhi accused the Pakistani state of refusing to participate.
Both India and Pakistan claim all of Muslim Kashmir, but control only parts of it.
The two countries have had three wars and a limited conflict – all but one were about Kashmir.