According to a 1995 report published in The Nonproliferation Review, Surya (meaning the Sun in Sanskrit and many Indian languages) is the codename for one of the Intercontinental ballistic missiles that India is reported to be developing, for which there is no formal statement from India.
[4] According to the report, the Surya is an intercontinental-range, surface-based, solid and liquid propellant ballistic missile.
The report adds that Surya is the most ambitious project in India's Integrated Guided Missile Development Programme.
The Surya missile is more strategic in nature due to its capabilities and thus gives enemy mutually assured destruction.
[4] According to a 2013 report by The New Indian Express, Surya missile is speculated of being built highly confidentially under the code-name of Agni-VI.