At least four people were injured Sunday when suspected Bodo insurgents triggered two grenade blasts in Chirang district of Assam, police said.Cadres of the National Democratic Front of Bodoland (NDFB) faction opposed to peace talks with the government lobbed a grenade in Deokurapar and another at the Ballamguri bus stand area in Chirang, about 250 km from the state's main city Guwahati and part of the Bodoland Territorial Area Districts.Four people were injured but their condition was stable, police said."We suspect the anti-talk faction of the NDFB to be behind the incident. There have been operations against the militants by police and security forces. The grenade blasts might be a retaliation by the militants," a senior police official said.