The latest's vessel seized by pirates, the MS Lugela, has 12 Ukrainian crewmembers onboard and was carrying a cargo of steel when it came under attack after leaving the dangerous waters of the Gulf of Aden, Press TV reported.
A spokesman for the European Union's anti-piracy mission Atalanta said the Panama-registered freighter had sent a distress signal to its Greek operator on Saturday.
Shortly afterwards, all contact with the ship was lost, and the ship changed course in the direction of the Somali coast, where most likely it was anchored near the pirate hub of Harardhere.
With the monsoon season drawing to a close in one of the world's most dangerous and busiest maritime trade routes, the number of hijacking is expected to rise.
Tens of thousands of merchant vessels annually transit through the precarious Gulf of Aden waters to reach the Suez Canal.
Despite the presence of international anti-piracy forces, the number of attacks has continued to surge since 2007. The pirates, who usually demand millions of dollars in ransoms for hijacked vessel, are now holding 20 ships.