Police in Indian Kashmir say six people were killed and at least 21 others injured in an explosion aboard a tourist bus in the summer capital, Srinagar.

Local authorities say the bus was carrying Muslim tourists from the western Indian state of Gujarat to the popular tourist destination of Shalimar Garden Sunday afternoon when the blast occurred.

The cause of the explosion is not clear, but authorities are not ruling out an attack by Kashmir separatists.

Last year, at least 12 Indian tourists were killed and dozens wounded in a series of bombings by suspected separatists.

Indian Kashmir is in the grip of an 18-year-long insurgency that has claimed more than 45-thousand lives. A number of rebel groups are fighting for an independent Kashmir or its merger with Pakistan.

Some information for this report provided by Reuters.