Rise in violence
A spokesman from the Pakistan-based group Jamiat-ul-Mujahideen called news organisations in Srinagar to say it had set off the blast, the Press Trust of India news agency reported.
There was no immediate independent confirmation of the claim.
Since 1989, more than a dozen armed groups have been fighting for Kashmir's independence from India or its merger with neighbouring Pakistan.
More than 68,000 people, mostly civilians, have been killed in the conflict.