He also said those incharge of terrorist infrastructure in Pakistan have resorted to other stratagems to infiltrate terrorists into India via Nepal and Bangladesh though it has not totally ceased via the Line of Control.

Addressing a day-long conference of Chief Ministers on the internal security, Singh said concerns may exist that the country's defence mechanism to thwart the numerous threats were inadequate and that there may be criticism that the range of instruments to deal with internal security threat were not sufficiently sophisticated.

"Clearly, there is need to review the effectiveness of our set up for the collection of technical signal and human intelligence. The training and equipment provided to our security forces also requires a careful review," he said.

Admitting that a great deal more needs to be done, Singh said both the Centre and the state governments must attend to this task with speed, efficiency and utmost dedication.

In his 30-minute speech, the Prime Minister referred to multi-dimensional challenges of different kinds of which the most serious threats were those posed by terrorism, Left wing extremism and insurgency in the Northeast.

"Extremism is primarily indigenous and home grown. Terrorism, on the other hand, is largely sponsored from outside the country, mainly Pakistan, which has utilised terrorism as an instrument of State policy," he said.

The Prime Minister said India's external policies have been dictated by a desire to have a supportive neighbourhood. "Unfortunately, we cannot choose our neighbours, and some countries like Pakistan have in the past encouraged and given sanctuary to terrorist and other forces who are antagonistic to India," he said.

Singh said India tried to minimise the impact of such hostility by fencing the border along LoC in Jammu and Kashmir from where the vast majority of the infiltrations into India tended to take place. Currently fencing was also going on at the border with Bangladesh, from where also a number of infiltrations have been reported.

"Consequent upon this, those in-charge of terrorist infrastructure in Pakistan have resorted to other stratagems to infiltrate terrorists into India. Infiltration is occurring from Nepal and from Bangladesh, though it has not totally ceased via the LoC. We are aware that the sea route is another option that is now being exercised. A few interceptions have taken place, though we failed to intercept the 10 Pakistani terrorists who came by sea from Karachi," he said.

A day after India presented evidence of involvement of elements based in Pakistan in the 26/11 Mumbai attacks to Islamabad and international community, the Prime Minister the Mumbai attack was carried out by a Pakistani based outfit Lashkar-e-Taiba.

"On the basis of investigations carried out (including by agencies of some foreign countries whose nationals were killed in the attack), there is enough evidence to show that, given the sophistication and military precision of the attack, it must have had the support of some official agencies in Pakistan," he said.

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’.

Both countries should not enter into a ‘blame-game’ and India should let Pakistan complete its investigations into the Mumbai attacks, Durrani told Dawn News channel.

He pointed out that Pakistan has already stated that it will not spare anyone found to be involved in the attacks.