Jorhat, Jan. 2: Three persons were injured, one of them critically, in a grenade explosion on the busy GNB Road in the heart of Tinsukia town this evening.

One of the injured was shifted to Assam Medical College and Hospital, Dibrugarh.

Police sources said suspected Ulfa militants, who came in a blue Maruti van, threw the grenade at a shop, Shankar Glass House, owned by Kishan Minda. But the grenade missed the target and exploded outside the shop, damaging glass panes. A car parked near the shop was also damaged.

An eyewitness said, “A car stopped in front of Shankar Glass House and one person got down to buy potatoes from a roadside vendor. As soon as he got back into the car, they threw the grenade and fled.”

The police have tightened security in and around the town and are trying to locate the vehicle in which the militants were suspected to have come.

Earlier in the day, troops of the army’s 18 Jat regiment recovered an improvised explosive device (IED), wrapped in a white polythene bag, from a Tata Winger passenger vehicle at Chabua in Dibrugarh district. The vehicle was going from Tinsukia to Dibrugarh.

The police have detained eight persons, including a woman, for questioning.

In another incident, army troops apprehended an Ulfa militant, identified as Hemkanta Changmai, at Lekhapni in Dibrugarh district today. An AK-81 was recovered from him.

Security forces have intensified vigil in Upper Assam given the recent spurt in Ulfa activity. The forces are also on the alert in the area for Maoists.