NEW DELHI  - India’s National Investigation Agency has been ordered to probe the alleged murder of two Indian fishermen by two Italian marines, an official said Monday, in a case that has strained diplomatic ties.

The decision to transfer handling of the case comes after the Supreme Court ruled in January that the Kerala government did not have jurisdiction to investigate the shootings, which occurred in waters off the southern coastal state.

The NIA, which is tasked with upholding Indian maritime law, “will launch a fresh probe and the case will be heard in a special court”, a senior home ministry official told AFP on condition of anonymity.

The two marines, Massimiliano Latorre and Salvatore Girone were serving as security guards on an Italian oil tanker when they shot the fisherman off the Kerala state port of Kochi last year. They said they believed the pair were pirates.

India’s Supreme Court granted the two men bail to fly home to vote in Italy’s recent elections — on condition they were sent back to New Delhi within a month.

Italy agreed and its ambassador signed an affidavit taking personal responsibility to return them, which led to fury when Rome announced that it was reneging on the deal.

The bitter diplomatic stand-off only ended when Italy performed a dramatic climbdown, returning the marines to New Delhi in March.

Italy had said the pair should be prosecuted at home because the shootings involved an Italian-flagged vessel in international waters, but India said the killings took place in waters under its jurisdiction. Under a prisoner transfer agreement between the two countries, the marines could serve their sentences in Italy if convicted.