ATHENS (Reuters) -A Greek naval court has charged 17 coast guard officers over one of the Mediterranean's worst shipwrecks two years ago, in which hundreds of people are believed to have drowned, three sources said on Friday.

The shipwreck of an overloaded migrant boat in international waters off the southwestern Greek town of Pylos on June 14, 2023, sent shockwaves across Europe and beyond. The naval court is still investigating the circumstances around the incident.

A coast guard vessel had been monitoring the boat, named Adriana, for 15 hours before it capsized and sank. It had left Libya for Italy with about 750 people on board. Only 104 of them are known to have survived.

Greek coast guard authorities have repeatedly denied any wrongdoing over the handling of the case.

Three legal sources said the 17 coast guard officers would be summoned by a judge to respond to accusations ranging from obstructing transport to causing or helping cause a shipwreck.

Contacted by Reuters, a Greek coast guard official said the service had not been officially informed about the charges and had asked to be briefed by the naval court.

Greece's judicial system has several preparatory stages and the compilation of charges does not necessarily mean that an individual will face trial.

Human rights activists and other protesters plan rallies across Greece on June 21 to mark the second anniversary of the Pylos shipwreck.

In February, the Greek Ombudsman recommended disciplinary action against eight coast guard officers, the first national probe into the incident to conclude.

Greece says that the coast guard operates with respect to human rights and that it has rescued more than 250,000 people since 2015, when the country was at the frontline of Europe's migration crisis.

(Reporting by Renee Maltezou and Yannis SouliotisEditing by Gareth Jones)