India's top court has ruled that the Italian ambassador Daniele Mancini enjoys no diplomatic immunity, and reiterated its earlier order preventing him from leaving the country.

New Delhi's Supreme Court said it has lost trust in Mancini after Rome refused to send back two marines charged with murdering two Indian fishermen at sea in February 2012.

"We don't trust the envoy anymore... we did not expect him to behave like this," said the judges, headed by Chief Justice Altamas Kabir.

The Italian envoy had claimed diplomatic immunity, citing Article 29 of the Vienna Convention which states: "The person of a diplomatic agent shall be inviolable. He shall not be liable to any form of arrest or detention. The receiving state shall treat him with due respect and shall take all appropriate steps to prevent any attack on his person, freedom or dignity."

However the Supreme Court responded by saying: "A person who comes to court and gives an undertaking has no immunity."

The court had earlier ruled that Mancini could not leave India, while the country's airports are maintaining high vigil to prevent his departure.

Mancini had given a personal undertaking to the court that the two marines would return to India after casting their votes in the Italian election. The court gave the marines a four-week window to visit their homeland, and this ends on 22 March.