Srinagar, Feb 14 (TIWN / IANS) At least 20 CRPF troopers were killed and some 25 others injured on Thursday when a van packed with explosives reportedly rammed into a CRPF bus on the Srinagar-Jammu highway in Jammu and Kashmir's Pulwama district, officials said.

In what is being described as one of the biggest loss to the security forces in one single incident, the Central Reserve Police Force (CRPF) bus was ambushed in Lethpora town, about 30 km from Srinagar.

The incident took place when some 2,547 CRPF personnel were coming in a convoy of 78 vehicles from the transit camp in Jammu and headed to Srinagar.

Police sources said a suicide attacker rammed his vehicle around 3.15 p.m., taking the security forces completely by surprise. An earlier report said an improvised explosive device (IED) was exploded and then militants fired at the convoy.

Jammu and Kashmir Police chief Dilbag Singh said it could well have been a suicide attack.

The Jaish-e-Muhammad (JeM) militant group claimed responsibly for the bloodbath.

In a statement to a local news agency GNS, a caller claiming to be a spokesman of JeM said it was a 'fidayeen' (suicide) attack.

As ambulances and security vehicles rushed the injured to hospitals, police sources said at least 10 of the wounded were in critical condition.

CRPF officials admitted that the bus which was the main target of the militants was destroyed fully and another CRPF vehicle was partly damaged.

"It is difficult to believe how anyone in the bus would survive," said one police officer.

Officials said the reason why so many CRPF personnel were on the move at one time was because the Srinagar-Jammu highway had been shut the past two days due to bad weather. The convoy left Jammu around 3.30 a.m.

One officer said earlier: "The IED had been planted inside a moving car on the highway and was detonated when the car came close to the CRPF bus."

Another officer said the CRPF and police would carry out a detailed investigation to understand the circumstances in which the attack took place.