Somali pirates said today that they had freed a Maltese-registered, Greek-owned ship that they hijacked more than six months ago as it sailed to the Middle East from Brazil.

But there were contradictory reports about whether the vessel had actually been released, and the Ukrainian government denied it.

The Ariana was carrying 24 Ukrainian crew when it was seized on May 2 north of the capital Mogadishu. The ship belongs to All Oceans shipping in Greece.

Last month, the pirates said they had agreed a $3.5 million ransom and expected to release the vessel soon.

"After days of negotiations we freed the Greek ship Ariana today," an associate of the gang named Abdinor told Reuters by telephone from the coastal town of Haradheere.

"It will be sailing away in the next few hours, I hope."

A senior diplomat at the Ukrainian embassy in Nairobi, Kenya, said the report was incorrect, but gave no other details.

Heavily armed Somali pirates have plagued the busy shipping lanes off the Horn of Africa for several years. Foreign warships from 16 countries are in the area to try to prevent hijackings.