About 30 crew members aboard the Zhenhua 4, a heavy lift ship registered in St. Vincent and the Grenadines, barricaded themselves in the ship's accommodation room as nine pirates boarded the vessel, according to Andrew Mwangura of the Kenyan Seafarers Association.
The crew radioed for help, and a coalition warship and two helicopters responded, firing on the pirates and forcing them from the ship about five hours after they boarded, Mwangura said.
Pirates hijacked three vessels Tuesday, Mwangura said, including the Malaysian tug Masindra 7, the Turkish cargo ship Bosphorus Prodigy, with a crew of 11 aboard, and a private yacht.
With the latest seizures, the gunmen are holding 18 vessels.
More than 124 incidences -- attempted and averted attacks and successful hijackings -- have been recorded up to this point in 2008, according to Mwangura.
A multinational naval force, including vessels from the United States, NATO member states, Russia and India, has been patrolling the Indian Ocean waters near the Gulf of Aden, which connects the Red and Arabian seas, following a sharp increase in pirate attacks in the region.