At least 15 people were injured in a bomb attack in India's north-eastern state of Assam on Thursday, hours after the government said it was considering tougher laws to combat attacks by militant groups.

A bomb planted on a bicycle exploded near a government office in Assam's Chirang district, some 230 kilometres west of the state capital Guwahati, the IANS news agency reported.

"Most victims were shoppers or office goers," the state's police chief Bhaskar Mahanta told the IANS as officials blamed the separatisit United Liberation Front of Asom 
(ULFA) for the attack.

Of the 15 injured moved to nearby hospitals, doctors said two were "critical."

A major rebel group in the state, the ULFA has been fighting for an independent homeland for the Assamese people since 1979. Official data shows that more than 10,000 people have been killed in the insurgency in Assam over the past two decades.

Besides battling separatist movements in its north-eastern regions and the northern Jammu and Kashmir state in 2008, India has seen a wave of bombings in which Muslim militants are believed to be involved.

The attack in Assam came 12 hours after Prime Minister Manmohan Singh chaired a special cabinet meeting Wednesday night in the aftermath of the weekend blasts in Delhi that claimed 24 lives.

Admitting there were "vast gaps" in intelligence gathering, Singh said his government was considering to strengthen laws to combat attacks by militant groups.

"We are actively considering legislation to further strengthen the substantive anti-terrorism law in line with the global consensus on the fight against terrorism," Singh said.

Singh, whose government has been flayed by opposition parties and the local media for being unable to tackle terrorism, maintained that Indian security agencies were successful in thwarting a number of militant attacks.

"But as the recent blasts in Jaipur, Bangalore, Ahmedabad, Surat and Delhi indicate, there are still vast gaps in intelligence. These need to be overcome," he said.

The Muslim militant group Indian Mujahideen claimed responsibility for the recent multiple bombings in Jaipur, Bangalore, Ahmedabad and Delhi where more than 140 lives were lost.

The Indian police believe that the Indian Mujahideen is a front for the banned militant groups Students Islamic Movement of India and the Pakistan-based Lashkar-e-Toiba.

India is among the countries worst affected by terrorism. More than 650 people have been killed in terrorist attacks in Indian cities over the past eight years.

The deadliest terrorist attack in recent years was in July 2006, when multiple bombings hit Mumbai's train network, killing 180 people.