Inspector General of Police Manish Kumar Sinha told reporters at the site that the militants hurled a grenade which “rolled under a parked bus before it went off”.
The injured were shifted to a government hospital.
Witnesses said the bus stand was teeming with people when the explosion occurred.
“At first, we thought it was a tyre burst. But when we approached the site, we saw people lying injured in critical condition,” said Sunil Kumar, 26.
The area was cordoned off by security forces.
Thursday’s is the third such attack at the Jammu General Bus Stand by militants in the last nine months.