Jaguar IS/IB (about 32 aircraft with 32 bombs from one squadron each at Ambala Air Force Station and Gorakhpur Air Force Station) aircraft, are believed to be assigned the nuclear strike role. Land-based ballistic missiles The estimated 68 nuclear warheads of land-based nuclear weapons of India are under the control of and deployed by the Strategic Forces Command, using a variety of both vehicles and launching silos. They currently consist of six different types of ballistic missiles, the Agni-I, the Agni-II, Agni-III, Agni-IV, Agni-V, Agni-P and the Army's variant of the Prithvi missile family – the Prithvi-I. However, the Prithvi missiles are less useful for delivering nuclear weapons because they have a shorter range and must be deployed very close to the India–Pakistan border. Additional variants of the Agni missile series have recently been inducted including the most recent, the Agni-IV and the Agni-V, which is currently being deployed. Agni-VI is also under development, with an estimated range of 8,000–12,000 km and features such as Multiple independently targetable reentry vehicles (MIRVs) or Maneuverable reentry vehicles (MARVs). Sea-based ballistic missiles The Indian Navy has developed two sea-based delivery systems for nuclear weapons, completing Indian ambitions for a nuclear triad, which may have been deployed in 2015. The first is a submarine-launched system consisting of at least four 6,000 tonne (nuclear-powered) ballistic missile submarines of the Arihant class. The first vessel, INS Arihant, was commissioned in August 2016. She is the first nuclear-powered submarine to be built by India. A CIA report claimed that Russia provided technological aid to the naval nuclear propulsion program. The submarines will be armed with up to 12 Sagarika (K-15) missiles armed with nuclear warheads. Sagarika is a submarine-launched ballistic missile with a range of 700 km. This missile has a length of 8.5 meters, weighs seven tonnes and can carry a pay load of up to 500 kg. Sagarika has already been test-fired from an underwater pontoon, but now DRDO is planning a full-fledged test of the missile from a submarine and for this purpose may use the services of the Russian Navy. India's DRDO is also working on a submarine-launched ballistic missile version of the Agni-III missile, known as the Agni-III SL. According to Indian defence sources, the Agni-III SL will have a range of . The new missile will complement the older and less capable Sagarika submarine-launched ballistic missiles. However, the Arihant class ballistic