NEW DELHI - India’s airports were put on alert Friday to prevent Italy’s ambassador from taking flight, in a dramatic escalation of a dispute over two Italian marines who skipped bail while on trial for murder.

A source in the home ministry told a French news agency that an order had been faxed to immigration authorities at all the country’s international airports telling them that “Daniele Mancini should not leave without permission”. Another senior official in the department said the ministry “is just following the Supreme Court’s order of preventing the Italian ambassador from leaving India”.

“He will have to inform the immigration authorities if he wants to leave the country,” the official told AFP on condition of anonymity.

The Supreme Court on Thursday directed that Mancini, who had negotiated a deal for the marines to return home to vote in last month’s Italian election, should stay in India until the next hearing about the dispute on Monday.

Rome announced earlier in the week that it was reneging on commitments to send back Massimiliano Latorre and Salvatore Girone, who face murder charges over the death of two Indian fishermen in February last year.

Mancini signed an affidavit giving his personal assurance that the two marines would return.

The Supreme Court ruling appeared to run contrary to diplomatic norms guaranteeing the freedom of movement of foreign envoys and risks a further souring of relations between Rome and New Delhi.

Article 29 of the Vienna Convention on Diplomatic Relations of 1961 states that diplomats shall “not be liable to any form of arrest or detention”. But referring to Mancini’s affidavit, India’s foreign ministry has argued that “if the diplomatic agent willingly submits to the jurisdiction of a court, then that jurisdiction applies”.

Diljeet Titus, a lawyer who is acting for the Italian government and the two marines following the resignation of another attorney, refused to comment on the alert order.

Meanwhile, Times of India, quoting sources, said India was downgrading its diplomatic ties with Italy and had asked its ambassador-designate to that country Basant Kumar Gupta, who was scheduled to leave for Rome on Friday, not to proceed to take up his posting.

“The decision of not sending Mr Gupta to assume his position is tantamount to the fact that India wants to keep diplomatic ties with Italy at a level lesser than the ambassador,” said TOI.

Meanwhile, all the exit points, including airports across India were alerted to prevent Italian ambassador Daniele Mancini from leaving the country. The decision was taken by the Union home ministry a day after the Supreme Court restrained the Italian ambassador from leaving India without its permission, official sources said.

The marines shot dead the fishermen off India’s southwestern coast when a fishing boat sailed close to an Italian oil tanker they were guarding. They say they mistook the fishermen for pirates.

Italy insists the marines should be prosecuted in their home country because the shootings involved an Italian-flagged vessel in international waters, but India says the killings took place in waters under its jurisdiction.

Relations between the two countries have also been soured by corruption allegations surrounding a $748 million deal for the purchase of 12 Italian helicopters which the Indian government is now threatening to scrap.

The dispute has been a major embarrassment for the Indian government and Prime Minister Manmohan Singh, who has warned of “consequences” for bilateral ties if the pair does not return to stand trial in New Delhi.

Singh’s rivals have accused the government of incompetence by allowing the marines to go home while facing such serious charges, and the main opposition Bharatiya Janata Party says Italy is treating India “like a banana republic”.

The Hindu-nationalist BJP has also implied untoward motives by Sonia Gandhi, the Italian-born head of India’s main ruling Congress party.

On Thursday, Indian Foreign Minister Salman Khurshid discussed the issue with ambassador Joao Cravinho, the head of the European Union’s diplomatic mission.

“He was briefed about the entire issue. It was important to keep him informed,” said an Indian government official.