The incident of gas leakage took place at about 5:00 PM while the ship was undergoing maintenance repairs.
Maintenance work was being undertaken in the Sewage Treatment Plant (STP) compartment. Due to inhalation of the toxic fumes, four personnel (two naval sailors and two civilian workers) were evacuated to Naval Hospital at Karwar, a statement by the Navy said.
Two personnel, namely Rakesh Kumar Shipwright Artificer Class 4, and Mohandas Kolambkar, an employee of Royal Marine, succumbed due to gas inhalation, it said.
The Navy has ordered an inquiry into the incident and action has been taken to render the compartment and area on the ship safe.
INS Vikramaditya is India's largest naval ship and equipped with a variety of integral weapons and sensors and it was undergoing maintenance repair since June 1.