Srinagar/New Delhi, (PTI) Security forces have launched a massive hunt for Pakistani national and Lashkar-e- Taiba (LeT) commander Abu Ismail who has emerged as the mastermind of the deadly terror attack on Amarnath pilgrims, a senior police official said here today.

The government has also sounded the "highest alert" across Jammu and Kashmir in the wake of Monday's attack in Anantnag district of Kashmir in which seven Amarnath pilgrims, including six women, were killed.

Officials in Delhi, quoting intelligence inputs, said four terrorists, two of them Pakistanis, are suspected to have been involved in the attack.

Ismail was the mastermind of the attack and he was assisted by another Pakistani and two local militants, they said.

Ismail has been active in Valley for several years and had moved base to south Kashmir more than a year ago, the police official said in Srinagar.

Proactive operations have been launched, mainly in south Kashmir, to track down Ismail as investigations including communication intercepts have pointed to his involvement in the attack on the pilgrims, he said.

The official said the attack in Anantnag appears to be reprisal for killing of several LeT terrorists including top commander Bashir Lashkari in an encounter with security forces earlier this month.

"The terrorists are frustrated at the back-to-back losses suffered by them during counter-insurgency operations over the past month or so and have now resorted to attacking civilians and tourists," he said.

A home ministry offical indicated in New Delhi that the anti-terror operations in Jammu and Kashmir would be intensified as he said the security agencies have been told to implement security plans with full vigour.

The Anantnag attack on the pilgrims came on the same day when police announced arrest of a module of LeT including a Hindu terrorist hailing from Muzaffaranagar in Uttar Pradesh.

Targeting of the pilgrims has led to a massive outrage in Kashmir, with people of the Valley saying that such incidents go against the concept of composite culture and Kashmiriyat.

Meanwhile, as the annual pilgrimage continues, the central government issued the "highest alert" in Jammu and Kashmir.

The alert was issued after a central ministerial team comprising Minister of State in the PMO Jitendra Singh and Minister of State for Home Affairs Hansraj Ahir visited Kashmir and held extensive discussions with the top brass of the security establishment, Governor N N Vohra and Chief Minister Mehbooba Mufti on the prevailing situation.

"Considering the unfortunate loss of life and injuries suffered by the yatris (pilgrims) in the recent terror attack, the entire security apparatus has been put on the highest alert by the ministers," a home ministry statement said.

The ministers visited Srinagar following a directive from Prime Minister Narendra Modi and Home Minister Rajnath Singh.

They discussed the security situation in detail with the chief minister and the governor, before holding an in-depth security review with the local army commander, the chief secretary, the police chief and senior officers of the state government, the DG of the CRPF, and senior officers of BSF and other security agencies, the statement said.

The central ministers stressed that the entire country was with the Kashmiris and the pilgrims and that all arrangements for a safe and secure pilgrimage would continue with renewed vigour.

So far, more than 1.5 lakh pilgrims have visited the cave shrine located in the mountainous region of south Kashmir. The 40-day long pilgrimage will conclude on August 7.

The home minister yesterday took stock of the situation in Kashmir Valley, particularly on the routes to the shrine located in the Himalayas at an altitude of 12,756 feet, during an hour-long meeting.

As many as 21,000 paramilitary personnel in addition to state police forces have been deployed for security of the pilgrimage routes.