Somali pirates have freed four South Korean seamen who were held ransom for 19 months, with the ex-hostages aboard a South Korean warship in the Gulf of Aden on Sunday, the Yonhap news agency reported. The warship was in the sea between Somalia and Yemen as part of a multinational anti-piracy mission. The South Korean sailors were in good condition. Their destination was not disclosed. Their merchant ship, the MT Gemini, was hijacked by pirates on April 30, 2011. The ship's Singaporean owner agreed with the pirates on terms for their release, the Foreign Ministry in Seoul said, without giving further details. Yonhap quoted a ministry official saying the Foreign Ministry assisted in the ransom negotiations. The pirates released all the other nationalities in the 21-member crew within seven months of the seizure of the ship, and also let the ship itself depart.