Prabhakar Tripathy, a spokesman for the Central Reserve Police Force, said: "We are verifying from where the grenade was lobbed."
Also on Friday, a police post at Sheeri, a village 70km north of Srinagar, was fired on killing one policeman and critically wounding another four, Viplav Kumar, a senior superintendent of police, said.
No one has claimed responsibility for the two attacks.
Several hours earlier, an improvised explosive device was triggered as an army bus passed by in a high-security zone in Srinagar, Sajjad Ahmed, a police officer, said. The 15 wounded soldiers were hospitalised, one in critical condition.
In a statement faxed to the local Kashmir News Service, Ahsan Illahi, spokesman for Hezb-ul-Mujahedeen, claimed his group's responsibility for the attack.
|The Indian army said it shot dead four|
suspected separatists on Thursday [AFP]
Meanwhile, the army said that troops shot dead four suspected separatists in two battles late on Thursday in Pulwama and Udhampur districts, in the south of the disputed region.
Hezb-ul-Mujahedeen is one of a dozen armed groups which have been fighting since 1989 for Kashmir's independence from India or its merger with Pakistan.
More than 68,000 people, mostly civilians, have been killed in the conflict.
India and Pakistan have fought two wars over control of Kashmir since they won independence from Britain in 1947.
The longtime rivals have been holding talks since 2004 to settle the Kashmir dispute, but without success so far.