India is also procuring S-400 Triumf air defence missile systems at a cost of nearly Rs 40,000 crore

India is working on a mega defence project to make the airspace over almost all its major cities, including Delhi and Mumbai, virtually impregnable, sources in the military establishment said.

The government is procuring a variety of air defence systems, including missiles, launchers and command-and-control units from the US, Russia and Israel, besides deploying indigenously developed missiles as part of the project, they said.

In the last few years, China has significantly ramped up its air power and sources said that the government was determined to equip the Indian Air Force with capabilities on par with its adversaries.

"Missile shield over the national capital and many other cities are being strengthened considering the evolving security scenario. Procurement of missile systems, radars and weaponry is part of the initiative," a senior military official said.

India is engaged in talks with the US for procuring components of air defence systems, including missiles, radars and drones, and attack helicopters. The US has already approved sale of 22 Sea Guardian drones to India at an estimated cost of USD 2 billion.

It is for the first time the US is selling the drones to a country which is not a member of the North Atlantic Treaty Organization (NATO).

Sources said India is also looking at the US' National Advanced Surface to Air Missile System-II to bolster its own missile shield.

India is also procuring the S-400 Triumf air defence missile systems from Russia at a cost of nearly Rs 40,000 crore to boost its air defence mechanism. The deal is likely to be signed by the two countries later this year.

"The aim of the project is to make our skyline impregnable," the official said.

As part of efforts to strengthen the country's aerial security, India is in the process of inducting the first batch of its intercontinental ballistic missile system -- Agni V -- which is expected to significantly bolster the country's air defence system. The missile, with a strike range of 5,000 km, is capable of carrying nuclear warhead.

A very few countries, including the US, China, Russia, France and North Korea, have intercontinental ballistic missiles.

In its missile armoury, India currently has Agni-1 with a 700 km range, Agni-2 with a 2,000-km range, Agni-3 and Agni-4 with 2,500 km to more than 3,500-km range.

In November last, India successfully test fired air-launched variant of the Brahmos, the world's fastest supersonic cruise missile, from a Sukhoi-30 combat jet. The missile will be also be part of the project to make the country's airspace impregnable, the sources said.

The Defence Ministry is now expediting the process to integrate the Brahmos missile with 40 Sukhoi combat aircraft.