An Indian citizen sentenced to death for spying in Pakistan has filed a mercy petition with Chief of Army Staff General Qamar Bajwa, Inter-Services Public Relations (ISPR) said on Thursday.

Former Indian naval officer Kulbhushan Jadhav was arrested last year in Balochistan, the site of a long-running conflict between the Pakistan military and separatist insurgents.

"Commander Jadhav has admitted his involvement in espionage, terrorist and subversive activities in Pakistan and expressed remorse at the resultant loss of any precious lives and extensive damage to property due to his actions," ISPR said in a statement, adding that he has asked for mercy on "compassionate grounds".

After Jadhav was sentenced to death in April, India asked the World Court for an injunction to bar the execution, arguing that he was denied diplomatic assistance during what it terms as an unfair trial.

The World Court, formally known as the International Court of Justice, ordered Pakistan in May to delay Jadhav's execution. It argued that Islamabad violated a treaty guaranteeing diplomatic assistance to foreigners accused of crimes.

The World Court is the top United Nations legal body for hearing disputes between states and its rulings are binding - though occasionally flouted.

Pakistan authorities say Jadhav confessed to being assigned by India's intelligence service to plan, coordinate and organise espionage and sabotage activities in Balochistan "aiming to destabilise and wage war against Pakistan".

Balochistan, which has rich reserves of natural gas and minerals, is also at the centre of $57-billion Chinese-backed "Belt and Road" development project that first focused on Chinese firms building roads and power stations but is now expanding to include setting up industries.

Pakistan also released a second confession from Jadhav. In this he admits to working for India's Research and Analysis Wing (RAW) and financing Baloch separatists to carry out attacks on Pakistani military targets.