An Indian Air Force (IAF) pilot is "missing in action" and a Pakistani fighter jet has been shot down, New Delhi said on Wednesday as fears of war darkened India-Pakistan relations with Islamabad launching retaliatory strikes and claiming it has arrested two Indian pilots in its territory.

In Pakistan, Prime Minister Imran Khan tried to defuse the tensions by saying that war is futile and can lead to unknown consequences while making an oblique reference to the nuclear weapons that both countries possess.

A day after India bombed Jaish-e-Mohammed's biggest training camp in Pakistan, it was a morning of developments moving with dizzying rapidity. Islamabad claimed it hit back at India by bringing down two Indian military aircraft, one of which crashed in Pakistan occupied Kashmir while the other fell in Jammu and Kashmir.

Officials in New Delhi said a Pakistani Air Force F-16 fighter jet was shot down by Indian air defence forces in Jammu region's Rajouri sector. During the encounter, a MiG 21 was lost and the pilot was missing.

As tension mounted, the entire airspace north of New Delhi was briefly "vacated". Nine airports in Jammu and Kashmir, Himachal Pradesh and Punjab were closed for civilian traffic for some part of the morning but opened later in the day.

To take this discussion forward, CNBC-TV18 spoke with Vivek Katju, former secretary for the ministry of external affairs and Vinod Patney, retired Air Marshal.

According to Katju, "The Pakistani action today was provocative and escalatory. We had not struck any target of the state of Pakistan military or civil, we had struck a terrorist facility and it was a preemptive strike. We had played it very low key. "

Patney said, "As far as walk the talk is concerned, does anybody believe that Pakistan and its Prime Minister will indeed walk the talk towards peace. We would be naïve to even imagine that. However, one is not sure if Pakistan will stop at the limited action taken by them today or will they escalate and for that, we would have to wait and watch."