Eight Sri Lankan crew members were on board the Aris 13 when it was hijacked off the coast of Somalia on Monday
Pirates on board a hijacked oil tanker anchored off the Somali coast have fired shots on maritime forces.
Eight Sri Lankan crew members were on board the Aris 13 when it was taken over on Monday.
The European Union anti-piracy operation in the region announced on Tuesday that the armed men were holding the crew captive - and demanding a ransom for the ship's release.
The crew are reportedly being held in a locked room onboard and have been cut off from communication lines.
An official from the Somali maritime forces said: "We tried to intercept a boat that was carrying supplies to the pirates, but pirates on the ship fired on us and so the pirate boat escaped."
One pirate named as Abdulaahi claimed the pirates have killed a member of the marine force and injured another - but the official has dismissed the claim.
Residents near the ship in the semi autonomous region of Puntland reported hearing gunfire.
Negotiations have been taking place in an attempt to "free the boat without condition", but authorities have warned they will attack the hijackers if efforts by local elders to get them to surrender are unsuccessful.
Families of the eight crewmembers yesterday pleaded for the men to be released unharmed – while the pirates demanded a ransom.
Somali pirates usually hijack ships and crew for ransom - and do not normally kill hostages unless they come under attack.
This is the first hijacking in the region for five years - and maritime experts have accused ship owners of becoming complacent after a long period of calm.
Attacks have fallen off sharply since 2011, after ship owners tightened security and vessels held further away from the Somali coast.
The hijacking on Monday was the first such seizure of a large commercial vessel off Somalia since 2012.
Somalia's foreign ministry has said it is working to help ensure the "safety and welfare" of the crew members.
Additional reporting by IRN ...