Three days after a bomb blast at Delhi High Court killed 13 people, Prime Minister Manmohan Singh on Saturday admitted that a section of the country's youth had been radicalised, but said no ideology could justify violence.

"We need to identify and address the causes of radicalisation of some of our youth," Singh said at the 15th National Integration Council (NIC) meeting.

"The problems of terrorism and leftwing extremism constitute two major challenges that our society and polity face today. The terrorist attack in Delhi last Wednesday is a stark reminder to us that there can be no let up in our vigilance," he said.

"Time and again, our nation has been subjected to terrorist violence. Terrorists seek to justify such violence based on misplaced sense of ideology.

"The institutions and instruments of our democratic polity allow sufficient opportunity for articulating differing points of view without recourse to violence," the prime minister said.

The NIC meet, happening after three years, discussed measures to promote communal harmony, eliminate discrimination, especially against minorities and Scheduled Tribes, and ways in which the state and police should handle civil disturbances.

Singh asked the NIC to unequivocally send out a message that violence cannot be justified under any circumstances and reaffirm the nation's collective resolve to fight it in all its manifestations.

"No civilised society can tolerate or endorse loss of innocent lives in the pursuit of any ideology," he added.

Singh chose the occasion to point out that lack of productive employment opportunities was one factor leading to radicalisation of youth.

He also listed out the social welfare schemes of the government such as the national rural employment guarantee programme; the land acquisition, resettlement and rehabilitation bill; rural health mission; Bharat Nirman projects; forest rights and right to education legislations as some of the measures to wean away young men and women from radical movements.

Expressing "great satisfaction" that inter-community relations in recent years have by and large remained harmonious, the prime minister said NIC members had played an active role in ensuring that people responded with maturity to developments that may otherwise flare up communal tempers.

"Nevertheless, we need to maintain a continuous vigil in this regard. We also need to recognise that members of the minority communities often have a perception of being unfairly targeted by law enforcement agencies in the aftermath of unfortunate incidents," he said.

"While law must take its own course, we need to ensure that our investigating agencies are free from biases and prejudices of any kind. The media also has to play an increasingly important and constructive role in promoting peace and harmony in our society," he added.

On the law enforcement front, the prime minister said there must be a continuous upgrade and strengthening of the investigating agencies and intelligence gathering apparatus to deal more effectively with newer methods and technologies that the terrorists and Maoists adopt.

"In the last few years, we have tried hard to achieve this," he said, listing out measures such as the National Intelligence Grid, called the NATGRID, being implemented to access all intelligence sources and analysis to identify actionable points.

Noting that the National Investigation Agency (NIA) had begun investigating terrorist-related crimes in the right earnest, he said of the 29 cases handed over to the NIA, charge sheets were filed in 20 cases.

"Security from internal and external disturbances is a sine qua non for a nation state and steps to ensure this have always been accorded the highest priority in government. Security matters have been regularly reviewed and discussed jointly with state governments," he said.

"We have also taken up security issues with our neighbours, and I am happy that some of our neighbours have extended cooperation, which has proved helpful in controlling violence in the northeast," he said.

"However, concerns remain and these will continue to be addressed," he added.