In a diplomatic and legal victory for India, the International Court of Justice (ICJ) on Thursday stayed the execution of alleged spy Kulbhushan Jadhav, dismissing Pakistan's contention that it had no jurisdiction to go into the matter.

In a unanimous and binding decision, the UN's top court said the status quo should be maintained pending final decision to be taken in the case that has brought ties between the two rival neighbours to a new low.

"Pakistan shall take all measures at its disposal to ensure that Jadhav is not executed pending the final decision in these proceedings and shall inform the court of all the measures taken in implementation of the present order," ICJ President Ronny Abraham said, reading out the order in the open court.

"The court also decides that until it has given its final decision, it shall remain seized of the matters which form the subject matter of this order," said the court which consists of 10 judges, including Justice Dalveer Bhandari of India, besides President Abraham.

Jadhav was allegedly arrested from Pakistan's restive Balochistan province on March 3, 2016. Pakistan claimed that the former Indian Navy officer confessed in a video that he was involved in spying and terror activities in Balochistan, a charge rejected by India. He was convicted in April by a Pakistani military court and sentenced to death.

India has maintained that Jadhav was abducted from Iran, where he was pursuing his business, and passed off as a spy.

India approached the international court on May 8 against Pakistan, accusing it of violating the Vienna Convention as Islamabad had rejected 16 requests by New Delhi seeking consular access. Pakistan was also accused of denying Jadhav a fair trial in violation of international human rights laws.

In a declaration appended to the judgment, Justice Bhandari concurred with the court on its interim order, saying: "...this is a case in which it regrettably appears, on a preliminary examination of the facts, that the basic human rights of Jadhav have been violated by not allowing India to have consular access to him after his arrest and during the pendency of the criminal proceedings against him in Pakistan."

The decision brought relief to India, with the Ministry of External Affairs calling the ruling "unanimous, favourable, clear and unambiguous". But Pakistan said it did not accept the UN court's jurisdiction in matters related to its national security.

External Affairs Minister Sushma Swaraj welcomed the ruling. She said the court order was "a great relief to the family of Kulbhushan Jadhav and people of India".

"I assure the nation that under the leadership of Prime Minister (Narendra) Modi we will leave no stone unturned to save Kulbhushan Jadhav," she said in tweets. Modi backed the Minister's statement, retweeting Sushma Swaraj's tweet from his personal account.

Foreign Affairs Advisor to Pakistan Prime Minister Nawaz Sharif, Sartaj Aziz, said the ICJ did not order Pakistan to provide consular access to Jadhav but has merely put forward an opinion.

He said a decision to provide consular access to Jadhav is yet to be made.

Pakistan Foreign Office spokesman Nafees Zakaria hit out at India for "trying to hide its real face" by taking the Jadhav case to the world court.

However, Pakistan Attorney General Ashtar Ausaf Ali's office in a statement indicated it would abide by the court's ruling while saying the interim order had "no bearing, whatsoever, on the final decision" related to the case.

"The ICJ has stated that by way of provisional measures, the status quo be maintained in the case of Jadhav. The court has clearly underscored that the provisional measures are without prejudice to the final determination of the merits and jurisdiction of the case."

The statement said Pakistan would take the case to the "logical end" and that India had no substance in the case.

In the two-page order, Justice Abraham also dismissed Pakistan's contention that the court had no jurisdiction over the case. It said Pakistan's alleged failure to provide consular access to Jadhav appeared to be falling within the scope of the Vienna Convention.

"In the view of the Court, this is sufficient to establish that it has prima facie jurisdiction under article I of the Optional Protocol. The Court further observes that the existence of a 2008 bilateral agreement between the parties on consular relations does not change its conclusion on jurisdiction," it said.

Justice Abraham said Pakistan had also failed to give any assurance that Jadhav would not be executed before the court delivered its final decision.

"The mere fact that Jadhav is under a death sentence and might therefore be executed is sufficient to demonstrate the existence of a risk of irreparable prejudice to the rights claimed by India. In those circumstances, the court is satisfied that there is urgency in the present case."