Agni- is an intercontinental ballistic missile being developed by the DRDO for the use of the Indian Armed Forces:

As you asking I am telling Missile scientist A.P.J. Abdul Kalam who had headed the SLV-3 project at ISRO, moved to DRDO to direct India's missile programme and about a dozen scientists accompanied Kalam from ISRO to DRDO, where he designed the Agni missile using the SLV-3's solid fuel first stage and a liquid-fuel (Prithvi-missile-derived) second stage, that’s the main contribution of ISRO .

Agni—I—II—III—IV—V—VI
Type Medium-range ballistic missile (Agni-I)
Intermediate-range ballistic missile (Agni-II, Agni-III, Agni-IV)
Intercontinental ballistic missile (Agni-V, Agni VI)
Place of origin India
Service history
In service (Tests) 11 April 1999, 17 January 2001, 29 August 2004 and 2 December 2014
Used by India
Production history
Manufacturer Defence Research and Development Organisation (DRDO), Bharat Dynamics Limited (BDL)
Unit cost 250 million (US$3.7 million) to 350 million (US$5.2 million) (Agni II)
Specifications
Weight 12,000 kg (Agni-I)
16,000 kg (Agni-II)
48,000 kg (Agni III)
22,000 kg [3] (Agni-III latest version)
17,000 kg (Agni-IV)
49,000 kg (Agni-V)
55,000 kg (Agni VI)
Length 15 m (Agni-I)
21 m (Agni-II)
17 m (Agni-III)
20 m (Agni-IV)
17.5 m (Agni-V)
Diameter 1.0 m (Agni-I, Agni-II)
2.0 m (Agni-III, Agni V)
1.1 m (Agni VI)
Warhead Strategic nuclear (15 kt to 250 kt), conventional HE-unitary, penetration, sub-munitions, incendiary, or fuel air explosives

Engine Single stage (Agni-I)
Two-and-half-stage (Agni-II)
Two stage (Agni-III) solid propellant engine
Operational
range 700–1,250 km (Agni-I)
2,000–3,500 km (Agni-II)
3,500–5,000 km (Agni-III)
Over 5,500 km (Agni-V)
8,000–10,000 km (Agni VI)
Flight altitude 300 km (Agni-I)
230 km (Agni-II),
350 km (Agni-III)
Speed 2.5 km/s (Agni-I)
3.5 km/s (Agni-II)
Guidance
system Ring laser gyro-INS (inertial navigation system), optionally augmented by GPS terminal guidance with possible radar scene correlation
Launch
platform 8 × 8 Tatra TELAR (Transporter erector launcher) Rail Mobile Launcher