Militants exploded a grenade at Digboi town. A man carrying the explosive suffered serious injuries. Four others were also injured.
Police said the United Liberation Front of Asom (ULFA) may have hired the person - Robin Rajbongshi, who works at a guest house - to lob the grenade at security forces.
However, it exploded while in his pocket.
While the condition of Rajbongshi is critical, the other four were stated to be out of danger, police said.
Later, another blast was triggered by suspected militants at Bengenakhowa in Golaghat district. Though no one was injured, the blast damaged the wall of Jalan Tea Factory.
Security has been intensified following intelligence inputs that cadres of ULFA opposed to peace talks between the rival faction and New Delh have been trying to sneak into the city.
"We have received intelligence that the anti-talk faction of Ulfa is trying to enter the city with two explosive laden Maruti vans," Senior Superintendent of Police A.P. Tiwari told IANS Saturday.
People have been asked to alert police about suspicious Maruti vans.
"We have intensified checking of vehicles and frisking of people across the city. All entry and exit routes are under strict vigil," Tiwari said.
Guwahati: Security has been tightened in Guwahati and in upper Assam following two consecutive bomb blasts which critically injured a man who was carrying a grenade, police said Saturday.
First Published: Saturday, September 15, 2012, 12:55