A powerful bomb killed at least 16 people, many of them schoolchildren, and wounded about 40 others as they assembled for an Independence Day parade Sunday in the northeastern state of Assam, authorities said.

Although no group asserted responsibility for the attack, Assam's chief minister and top elected official, Tarun Gogoi, told reporters he believed it was the work of separatist rebels from the outlawed United Liberation Front of Asom. The group, known as ULFA, is one of numerous separatist movements that for decades have been battling Indian security forces in the country's troubled northeastern Himalayan region.

"This is really a very tragic incident. It is most cowardly and inhuman," Gogoi said on national television. "Although we knew that ULFA activists were likely to attack, we did not have any specific report about this place. There appears to be an intelligence lapse."

Authorities said the blast occurred as schoolchildren gathered with teachers, parents and others at a college in the town of Dhemaji in Assam, a hilly, forested state known for its tea plantations and rich mineral deposits.

Witnesses described gruesome scenes of severed limbs and blackened corpses.

"The bomb exploded under the feet of the children," Jiban Saikia, a teacher, told the Reuters news agency. "There is blood and human flesh all over the ground."

The bloodshed came during one of the country's most prominent holidays, as India marked its independence from British colonial rule 57 years ago.

ULFA has been fighting for a separate homeland since 1979. More than 10,000 people have been killed in the conflict.

Authorities had been braced for trouble across the northeastern states, where about 150,000 police and paramilitary troops were deployed in advance of the national holiday.

Two other bomb blasts were reported in Assam on Sunday, but no one was hurt, police said. In addition, there were continuing protests in the northeastern state of Manipur over alleged human rights abuses by army forces deployed to fight another insurgency there. One protester set himself on fire and was rushed to a hospital with burns.

The conflicts with ULFA and other such movements in the northeast are distinct from the better-known separatist insurgency in the Himalayan province of Jammu and Kashmir, where Indian forces have been battling Islamic militants supported by Pakistan since 1989.

In Kashmir's Baramulah district on Sunday, militants fired a grenade at a school during an Independence Day event organized by the Indian army, wounding 16 people, officials said.

Security forces were also on high alert in the capital, New Delhi. Authorities closed airspace above the city, blocked streets and deployed tens of thousands of police and paramilitary troops to guard against terrorist attacks.

Speaking at the capital's historic Red Fort, India's new prime minister, Manmohan Singh, said his government would "fight terrorism forcefully" but added that he was ready for talks with any group that would give up its weapons. Singh said militant violence in Kashmir was hindering peace negotiations with Pakistan, but he pledged to continue the talks with "firm resolve and sincerity."

The bombing in Assam triggered a wave of protests as people took to the streets, some of them setting government vehicles afire as police fired weapons into the air. The bombing came a day after a grenade attack killed one person and injured 19 at a movie theater in the town of Gauripur in Assam.

Earlier in the day, Gogoi, the chief minister, unfurled the Indian flag in Guwahati, the state's commercial capital, while asserting that the government was committed to holding talks with the separatists.

A girl injured in the bombing is treated at the Assam Medical College Hospital. About 40 people were wounded by the powerful blast.