Five persons, including three women, were killed and 75 others injured when the proscribed United Liberation Front of Assam struck with vengeance by triggering an explosion at the weekly market at Kumarikata in Baksa district of Assam bordering Bhutan hills at around 1.20 pm on Sunday. The bomb was planted on a bicycle.

A senior Assam police official said that the blast, a handiwork of the 709 battalion of the ULFA, was a vivid reflection of ULFA's frustration over the crack that has surfaced in the outfit in the wake of unilateral ceasefire declared by 'A' and 'C' companies of the 28th battalion of the outfit last week.

The police said four persons including three women were killed on the spot while a seriously injured person died on the way to Guwahati Medical College Hospital. Police recovered another bomb planted in the market immediately after the blast.

Twenty-three injured persons, including eight grievously injured, were rushed to the GMCH in Guwahati.

The explosion took place in the corner of the market where some Bodo tribal traders were selling pork. The market was teeming with people at the time of the explosion.

The area is a known bastion and refuge of militants belonging to the 709 battalion of the ULFA.

The police suspected that under extreme pressure from the outfit's top leaders who are out to take revenge for the split engineered in its ranks by the security forces, the cadres of the 709 battalion triggered the blast within their den itself after failing to pierce the mounted vigil in urban centres of the state.

Tension has gripped the area, which is inhabited by people from Bodo tribe and tea tribes, following the blast even as the police and the army have mounted vigil.

A red alert has been sounded all over the state in the wake of Sunday's blast as security forces apprehend that ULFA militants may try to strike terror in other parts of the state. Police have set up additional checkpoints in and about Guwahati.