Police said the two unidentified men open fired at the security guards outside the ISRO campus, after they were interrogated by the guards, when they were seen moving around in a suspicious manner.
The men escaped from the spot after exchanging fire with the security guards.
However, ISRO officials have ruled out terror angle in the attack.
Meanwhile the Home Ministry has sought a report on the sequence of events in the incident and has entrusted the security of the facility to the Central Industrial Security Force.
The attack came after the Home Ministry had warned ISRO of possible terror attack.