NEW DELHI (AP) — India’s Supreme Court barred Italy’s ambassador from leaving the country Thursday and demanded that he explain why his country is refusing to return two Italian marines to stand trial for the killing of two Indian fishermen, a government official said.

The court had allowed the marines to go home in February to vote in national elections and to celebrate Easter with a written promise from Italian Ambassador Daniele Mancini that they would return to stand trial. Italy announced Monday that it would not send them back.

The dispute has damaged relations. Indian Prime Minister Manmohan Singh said there would be consequences if Italy does not back down.

Indian Foreign Minister Salman Kurshid said the matter "will be treated with urgency and it will be treated with determination to ensure that we don’t suffer."

Kurshid said the government would wait for the Supreme Court to make a ruling.

The court demanded Thursday that Italy explain why it was reneging on its promise, banned Mancini from leaving India without its permission and insisted he file his response by Monday.

Indian External Affairs Ministry spokesman Syed Akbaruddin said India expected Italy to respect the agreement that its ambassador voluntarily submitted to India’s top court.

"That’s the issue at stake. Everything else takes a secondary importance," Akbaruddin told reporters.

He said India was reviewing its relations with Italy. "We will take further action that is appropriate, taking into account all aspects of our relations," Akbaruddin said.

The marines, Massimilian Latorre and Salvatore Girone, were part of a military security team aboard a cargo ship when they opened fire on a fishing boat in February last year, killing the two fishermen. The marines said they mistook the boat for a pirate craft.

Italy maintains that the shooting occurred in international waters and that Rome should have jurisdiction. India says the ship was in Indian territorial waters.

The Italian Foreign Ministry said in a statement Monday that Italy would not return the marines because India’s decision to try the pair there would violate their rights, in particular the principle of immunity for foreign state actors. The ministry said it would be open to international mediation.

Singh told Parliament on Wednesday that Italy’s actions "violate every rule of diplomatic discourse" and said they had damaged bilateral relations that were built on trust.

A spokesman for U.N. Secretary-General Ban Ki-moon said Wednesday that he called on both sides to peacefully resolve their issues in accordance with international law. Italian Foreign Minister Giulio Terzi welcomed Ban’s statement and said Italy was prepared to reach a solution with India.