NEW DELHI (AFP) - India's embassy in Rome has received hate mail and even a live bullet, an official said on Friday, underlining fury in Italy over the prosecution of two Italian marines accused of killing two Indian fishermen.

India has consulted Italy over security at the embassy after recently receiving the mail as well as discovering the bullet in the embassy's mailbox, a foreign ministry official said in New Delhi.

"We are in diplomatic communication with Italy and hope that necessary safety and security is observed," foreign ministry spokesman Syed Akbaruddin told reporters during a weekly briefing in New Delhi.

Italy recalled its ambassador to India for consultations and summoned the Indian ambassador this week to express concerns over a delay in court proceedings against the two marines in New Delhi.

The moves again racheted up tensions between the two countries who were embroiled in a furious diplomatic row when the shootings took place in 2012.

Mr Akbaruddin said "we have a difference of opinion" over the case but discussions have been taking place to try to resolve the matter.

"We are communicating with them diplomatically. We have not yet made our views known public... but we have explained our views to Italy."

Italy this week described delays in prosecuting the marines as "unacceptable and indicate an Indian desire to procrastinate beyond all limits."

Indian legal experts have attributed the delay to uncertainty over which law to use to prosecute the men.

Italian authorities have lobbied the European Union and the United Nations on the case, saying the marines should be tried in Italy because it says the incident took place in international waters.

India denies this, saying it happened in Indian waters.