A house where suspected militants were holding up is seen in flames during a gun battle with Indian security forces in Pinglan village in south Kashmir's Pulwama district. Picture: Reuters/Stringer

Srinagar, India - India's top military commander in the disputed Kashmir region said on Tuesday Pakistan's main Inter-Services Intelligence (ISI) spy agency was involved in an attack last week on a security convoy claimed by a Pakistan-based militant group.

At least 40 paramilitary men were killed in the suicide car bombing on a Kashmir road on Thursday. The Pakistan-based Jaish-e-Mohammad (JeM) militant group claimed responsibility.

India has accused Pakistan of being behind the attack and tension has escalated between the nuclear-armed neighbours.

Pakistan condemned the bombing and denied any complicity, and on Tuesday it appealed to the United Nations to intervene, in light of the deteriorating security situation.

Lieutenant-General K.J.S. Dhillon told reporters that the leaders behind the attack were being tracked, and it had been orchestrated from the Pakistani side of the border.

"It was being controlled from across by ISI and Pakistan and JeM commanders," he said.

Dhillon did not provide any proof for his accusation.

He said he could not be more specific about the investigation into the blast and the suspected role of the Pakistan military intelligence agency, except to note its close links with the Jaish.

"The JeM is a child of the Pakistan army, and the ISI. The attack was masterminded by Pakistan, ISI and JeM," he said in Srinagar, the summer capital of Jammu and Kashmir state.

Pakistan demanded India conduct an open and credible investigation into the attack to back up its claims.

"Attributing it to Pakistan even before investigations is absurd," Pakistan's Foreign Minister Shah Mahmood Qureshi said in a letter to the U.N. Secretary General Antonio Guterres seeking U.N. involvement to lower tension.

"It is with a sense of urgency that I draw your attention to the deteriorating security situation in our region resulting from the threat of use of force against Pakistan by India," he said.

Indian Prime Minister Narendra Modi has promised a strong response to the attack which has caused outrage across the country and sparked calls for retribution.

India has long blamed Pakistan for the nearly 30-year revolt in Jammu and Kashmir, its only Muslim-majority state. Pakistan says it only provides moral and diplomatic support to the Kashmiri people in their struggle for self-determination.

Indian forces in Kashmir on Monday killed three militants, including the suspected organiser of the suicide bombing, officials said.

Jammu and Kashmir, a former princely state on the border between India and Pakistan, has been in dispute since the partition of India in 1947.

Control is split between the two countries but each claims the region in full.

The neighbours have fought three wars since 1947, two of them over Kashmir. They have fought countless skirmishes along their de facto border, which the United Nations monitors, in the Himalayan region.

Reuters