A passenger bus and another carrying paramilitary soldiers and their families were blown up in separate explosions in the insurgency-wracked Assam state (search) on Thursday, killing four people and wounding 39, officials said.

No group claimed responsibility for the blasts, but Inspector General of Police Khagen Sharma blamed militants of the United Liberation Front of Asom (search). The blasts came within hours of each other in the neighboring districts of Kokrajhar and Goalpara in western Assam.

The first bomb was hidden in an unclaimed piece of luggage and exploded as it stopped at Gossaigaon to let passengers off, said A.K. Bhutani, a local administrator. Gossaigaon is a town about 155 miles west of Gauhati (search), Assam's capital.

One passenger died at the scene and at least 33 others were injured, Bhutani said.

Hours later, another bomb exploded near Satipara village in Goalpara district, blowing up a bus carrying Border Security Force soldiers and their families. The bomb was planted under a culvert.

Two soldiers and a child were killed, and six others were injured, Sharma said. The soldiers were traveling with their families on holiday, he said.

Satipara is 125 miles west of Gauhati, Assam's capital.