One policeman was killed and three people were seriously injured when terrorists hurled a grenade at a police vehicle in the heart of Srinagar, summer capital of Indian-administered Jammu and Kashmir Tuesday afternoon.News agency Indo-Asian News Service quoting police officials said, the militants' target was a Jammu and Kashmir Police vehicle. Two civilians were seriously wounded in the explosion that created tension and panic in Srinagar. The blast also disrupted traffic movement in parts of the city. Police and paramilitary troops have launched searches for the terrorists, the agency said.