India successfully test-fires K-4 nuclear missile from submarine in Bay of Bengal

India has successfully test-fired an intermediate-range ballistic missile from a nuclear-powered submarine, marking a significant step forward in its sea-based nuclear deterrence capability.

The K-4 submarine-launched ballistic missile (SLBM) was launched from INS Arighaat during a test conducted in the Bay of Bengal off the coast of Visakhapatnam on Tuesday.

With a strike range of up to 3,500 km, the K-4 substantially strengthens India’s underwater nuclear strike capability. The missile was formally inducted into the Indian Navy in August 2024, placing India among a select group of countries that possess nuclear delivery capability across land, air, and sea.

Developed from the land-based Agni-III missile, the K-4 has been adapted for underwater launch. It is designed to eject from a submarine silo, rise to the ocean surface, and then ignite its rocket motor for flight. The missile can carry a nuclear warhead weighing up to 2.5 tonnes and is compatible with India’s Arihant-class submarines.

As a submarine-launched system, the K-4 represents the most concealed element of India’s nuclear triad. Ballistic missile submarines are engineered to operate silently for long durations, remaining hidden during deterrence patrols.

The ‘K’ series of missiles is named in honour of APJ Abdul Kalam, who played a pivotal role in shaping India’s missile development programme.