Timeline: How the migrant boat tragedy unfolded off Greece

A photo taken by the Greek coastguard hours before the tragedy shows a vessel crammed with people on its exposed decks. Some had their hands outstretched [Hellenic Coast Guard/AP]

Greek authorities have been accused of failing to rescue hundreds of refugees and migrants onboard a vessel that sunk near the coastal town of Pylos, causing one of the biggest tragedies in the Mediterranean Sea.

Reports suggest as many as 750 people were packed onto the fishing boat that capsized early on Wednesday in deep waters about 80km (50 miles) off the southern Peloponnese peninsula.