Three crew members of a Maltese-flagged supertanker, who were kidnapped by pirates three weeks ago off Nigeria, have been released, Greece’s foreign ministry said on Wednesday. The Kalamos crude carrier was heading to Nigeria’s main oil terminal when it was attacked on Feb. 3. The pirates killed the ship’s Greek deputy captain and escaped with three crew members—one Pakistani and two Greeks. All three are now safe and undergoing medical tests, the ministry said, declining to provide further information on their release. “We have asked the Greek ambassador in Nigeria to offer them accommodation and assist them with everything they need,” said foreign ministry spokesman Konstantinos Koutras. The ministry could not confirm reports that a ransom of $400,000 was paid. The vessel’s manager, the Athens-based Aeolos Management SA, was not immediately available for comment. The Kalamos tanker had been sailing at Qua Iboe, a waterway between Cameroon and Nigeria, when it was attacked, in an incident which highlighted the growing threat of violence off oil-rich West Africa.