The largest ransom ever paid to Somali pirates has been dropped onto the deck of a Greek-flagged oil tanker carrying two million barrels of oil.

The ransom delivered on Sunday is believed to be between $5.5m and $7m, according to unnamed sources interviewed by the Reuters news agency.

With 28 crew members on board, the Maran Centaurus oil tanker was captured in November as it was crossing the Indian Ocean, northeast of the Seychelles islands.

The tanker was sailing from Kuwait to the United States.

The European Union’s anti-piracy force says the crew includes one Romanian, two Ukrainians, nine Greeks and 16 Filipinos.

The EU has an anti-piracy force?