The European Union's anti-piracy naval force secured a ship on Friday that had been attacked off the coast of Somalia.
Armed assailants had attacked the vessel, run by Greek firm Latsco Marine Management, as it was travelling to South Africa from India on Thursday with 24 crew members aboard.
The Horn of Africa country was once notorious for its pirate raids and ransom attacks but incidents have become less frequent.
The pirates abandoned the merchant tanker after an "early show of force", an EU Naval Force statement said.
"The crew, composed of 24 people, is safe and no injuries have been reported."
An intense search for the pirates, who are believed to still be in the area, is underway, the naval force said, adding that they will be legally prosecuted if captured.
The United Kingdom Maritime Trade Operations (UKMTO) Centre earlier said the boat, the Hellas Aphrodite, was approached from the stern by a small vessel.
There was no security on board at the time of the attack, according to maritime news agency Lloyd's List.
The attack comes days after a failed attempt to board the MV Stolt Sagaland tanker off the coast of Somalia.
Four people attempted to seize the ship on Monday, according to a bulletin from the French Maritime Information Cooperation and Awareness Center (MICA).
The day before, a small boat approached the FV Intertuna Tres, but moved away after the ship sounded its sirens, according to MICA.
