European Union foreign policy chief Catherine Ashton today defended Italy's envoy to India, prevented from leaving the country due to a row over two Italian marines who skipped bail while on trial for murder in New Delhi.

A statement from Ashton's office said she "notes with concern" an Indian Supreme Court decision the previous day requiring ambassador Daniele Mancini to seek permission of the court to leave the country.

The 1961 Vienna Convention on diplomatic relations "is a cornerstone of the international legal order and should be respected at all times," the statement said.

Limitations to Mancini's freedom of movement "would be contrary to the international obligations established under this convention," Ashton added while urging the parties to find a mutually acceptable solution through dialogue.

India's top judge ruled that the envoy forfeited his diplomatic immunity over his role in securing the release of the pair who are accused of killing two Indian fishermen. Rome said India was breaking diplomatic conventions by ordering the envoy to stay in India until the next hearing in the case on April 2.

Chief Justice Altamas Kabir said Mancini, who had negotiated the Italians' release last month so they could vote in the Italian general election, had waived his immunity by giving an undertaking to a court that the pair would return.

The marines, Massimiliano Latorre and Salvatore Girone, are accused of shooting dead two fishermen off Kerala coast in February last year, when a fishing boat sailed close to the Italian oil tanker they were guarding.

They say they mistook the fishermen for pirates. The pair had been given permission to fly to Italy to cast their votes on the understanding that they would return, but the Italian government announced last week it would renege on its commitment to send the men back.