Somali pirates are believed to have captured a large cargo vessel off Oman, with 13 Iranian and 10 Indian crew on board, European Union naval forces said Sunday.

The seizure of the Sinin in the Arabian Sea took place late Saturday afternoon, 350 nautical miles East of Masirah, since when the boat has "changed course towards the Somali coast," EU-Navfor officials said in a statement.

The ship "sent out a distress signal, saying she was under attack," and aircraft despatched to the scene pictured "two suspected pirate skiffs on board." There has been no communication since, the European Union naval force said, including on the condition of the crew.

The Maltese-flagged and owned Sinin has a deadweight of 52,466 tonnes and was on route to Singapore from the United Arab Emirates.

Anti-piracy commanders are "monitoring the situation."