Guwahati, Mar 14 (IANS): Five ruling Congress workers were injured in a bomb blast at the party headquarters here Monday evening while eight BSF troopers were killed and five injured when their bus was targetted by Bodoland activists in Kokrajhar in Assam.

The two separate militant attacks took place in the northeastern state of Assam where elections are due April 4 and 11.

Congress party spokespersons Mehdi Alam Bora and Akshay Rajkhowa, and party general secretary Ranjan Bora were injured in the bomb blast at Rajib Bhawan in the heart of Guwahati. Two more Congress workers were also injured in the explosion.

The anti-talk faction of the outlawed United Liberation Front of Asom (ULFA) led by the elusive commander-in-chief Paresh Baruah has claimed responsibility for the attack at the Rajib Bhawan, located in the busy G.S. Road in Guwahati.

The blast occurred around 6.50 p.m. when the party office teeming with workers and leaders with assembly elections round the corner.

Earlier police said it was a grenade attack, but it was later confirmed a bomb was planted near the boundary wall of the party headquarter - concealed in a garbage bin.

In the second incident, tribal separatists of the anti-talk faction of the outlawed National Democratic Front of Bodoland (NDFB) ambushed a bus carrying 20 Border Security Force troopers around 8 p.m. near Ultapani in Kokrajhar district, about 220 km west of Assam's main city of Guwahati.

"The BSF bus was on its way to their base camp at Ultapani after carrying out a routine patrol when heavily armed NDFB militants opened indiscriminate gunfire from automatic weapons," a senior police official said.

Three BSF troopers were killed on the spot and ten injured. Five of the injured later succumbed to their injuries in a local hospital.

Five of the injured, three of them critical, are now in hospital with multiple bullet injuries.

"We suspect the NDFB anti-talk faction to be behind the attack," the official said.

No militant group has claimed responsibility for the ambush, but the NDFB is active in the area, police said.

ULFA's Paresh Baruah claimed responsibility for the attack.

"We claim responsibility for the blast and would like to warn the Congress party that we are still capable of attacking and the explosion is just a warning to them," Arunodoy Dohoti, publicity chief of the anti-talk ULFA faction, said in an emailed statement.

The anti-talks faction of the ULFA last month in an emailed statement threatened to attack Congress leaders and warned people against participating in party rallies in the run up to the assembly elections.

Describing the blast, Ranjan Bora told IANS "We were sitting inside the office when there was a deafening sound and the next moment I found myself bleeding with injuries in my face and neck."

A large portion of the Congress office was damaged in the impact of the blast - the roof and the wall of the office was ripped apart.

"We suspect it was a bomb planted just on the periphery of the Congress party headquarters," Assam police chief Shankar Baruah told journalists.

Assam Chief Minister Tarun Gogoi said the ruling Congress would never be cowed down to threats by ULFA hardliners.

"Threats to our leaders and workers by the ULFA is nothing new and let me make it very clear that we shall never be cowed down by such threats of attacks on our lives," the chief minister told journalists.

"I condemn this cowardly act and let me assure that we are going to step up security and take action against the ULFA in the strongest possible way."

The ULFA in the past has killed at least a dozen Congress leaders during elections beginning the 1996 assembly polls.

The ULFA statement last month said the Congress party was responsible for dividing the outfit - luring some leaders into holding peace talks with the government.

The first round of ULFA-government peace talks was held Feb 10 in New Delhi with the process being led by the outfit's chairman Arabinda Rajkhowa.

That the ULFA is vertically split was evident with Paresh Baruah terming the peace talks as 'unconstitutional' given the fact that Rajkhowa and other seven top leaders were being surrounded by 'Indian forces' - meaning the talks were being held under pressure from New Delhi.

But the pro-talk ULFA leadership led by Arabinda Rajkhowa has gone on record saying the decision to hold talks with the government had the sanction and approval of the ULFA general council.

A faction of the NDFB too is in peace mode by entering into a ceasefire with New Delhi.

Both the ULFA and the NDFB are fighting for independent homelands outside the Indian union.

More than 10,000 people have lost their lives to insurgency in Assam during the past two decades.