Referring to the existence of different concentric circles of terrorism impacting the country's security, the Prime Minister said the Mumbai terrorist attack fell into the category of one carried out exclusively by a foreign based outfit.

"There are other concentric circles of terrorism that often involve a combination of external forces backed by internal elements. There are still others which are essentially indigenous character," he said.

Singh said since the sea route was now being explored as an alternative to land routes, it had been suggested that there should be greater vigilance along the coast line and better monitoring of maritime activity in the territorial waters.

"The terrorists who carried out the attack on Mumbai used the sea route, and managed to evade our coastal surveillance," he said.

The Prime Minister said the recent pattern of terrorist incidents also suggested that increasingly the attack have a pan-Indian and trans-national aspect. "The terrorists are able to fashion new techniques and employ new skills. There is growing emphasis on 'mass causality attacks'," he said.

He said the terrorists were using modern communications skills. "Use of Internet and Voice over Internet Protocol connectivity, gives terrorists greater anonymity and makes detection difficult for the authorities," he said.

India, Pak should not indulge in blame-game: Durrani

Terming as ‘unfortunate’ Prime Minister Manmohan Singh's comments that Mumbai attacks must have had support of some Pakistani official agencies, Islamabad said the two sides should not indulge in a ‘blame-game’.

Mahmud Ali Durrani, Advisor to the Prime Minister on National Security, said he believed Singh's comments were ‘unfortunate’.

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