The warning by the United Liberation Front of Asom (Ulfa), which has been fighting for an independent Assamese homeland since 1979, came less than two weeks ahead of India's Indepe-ndence Day celebrations August 15.

Ulfa traditionally attacks key government installations in Assam such as pipelines rather than civilians. It usually carries out the attacks on August 15 -- Indepe-ndence Day.

But last year, the outlawed group detonated a powerful blast during a parade to mark the day, killing some 20 people, many of them youngsters.

"We cannot just sit tight with the hope of getting a positive response from the government for holding peace talks. We will intensify our armed struggle," Ulfa chairman Arabinda Rajkhowa said in a statement.

In July, Ulfa sent a letter to Indian Prime Minister Manmohan Singh saying it would enter peace talks if the government agreed to discuss its core demand for sovereignty.

The letter followed an invitation for talks by Singh in May aimed at ending an insurgency that has claimed over 10,000 lives.

"There was a lot of urgency shown by the government to get a formal letter from us for holding talks," said the Ulfa chairman. "But once we delivered the letter, the authorities have shown no urgency and that probably reflects their doubtful and insincere attitude in holding negotiations with us."

There was no immediate comment available from the federal government.

During a visit to the region late last year, Singh ruled out discussing independence, saying Assam was an "integral part" of India. He urged militants to abandon arms if they wanted to resolve the region's problems.

Security officials in Assam said they were concerned about a fresh upsurge in violence by Ulfa ahead of this year's Independence Day festivities.

"Intelligence reports indicate massive plans by Ulfa to create terror ahead of August 15," said a senior Assamese police officer, asking not to be named.

India's far-flung northeast is a cauldron of insurgencies.

The around 30 rebel groups, including Ulfa, who are fighting for autonomy or outright independence in the northeast accuse New Delhi of plundering the region's resources while neglecting its development.