Kulbhushan Jadhav's friends hoped Imran Khan will release him.

Retired navy officer Kulbhushan Jadhav's friends have appealed to Pakistan Prime Minister Imran Khan to release him, after the International Court of Justice or ICJ today asked the country to review his death sentence announced by Pakistan's military court on charges of "espionage" in 2017.

"Pakistan's prime minister (Imran Khan) had said he would create a naya (new) Pakistan. A new Pakistan will not be built by merely giving interviews, he will have to do something (to build a new Pakistan). He will have to take an initiative (to release Mr Jadhav)," Kulbushan Jadhav's friend Sachin Kale said in Mumbai.

After winning Pakistan's general election last year, Imran Khan in his inaugural address had promised to bring about a "naya" Pakistan.

"We have hopes from Imran Khan. If he releases Kulbhushan, it will strengthen our friendship with the country," another of Mr Jadhav's friends said.

Mr Jadhav's family lives in Mumbai.

Kulbhushan Jadhav's death sentence "should remain suspended until Pakistan effectively reviews and reconsiders the conviction and sentence," the world court said, agreeing with India that Pakistan had violated the Vienna convention by denying India consular access to the former officer convicted by a Pakistani military court.

"A continued stay of execution constitutes an indispensable condition for the effective review and reconsideration of the conviction and sentence of Jadhav," said the ICJ.

The world court said Pakistan had not informed Mr Jadhav about his rights, in a verdict read out at a public sitting of the United Nations court in The Hague.

"Pakistan deprived India of the right to communicate with and have access to Mr Kulbhushan Sudhir Jadhav, to visit him in detention and to arrange for his legal representation," said the UN court.

Kulbhushan Jadhav, 49, was arrested by Pakistan in March 2016 and accused of "espionage", a charge India has rubbished. A year later, Mr Jadhav was sentenced to death by a Pakistani military court.