South Korea on Friday sent a navy destroyer to the waters off Somalia to join an international patrol against pirates in the country's first naval mission abroad, Reuters reported. President Lee Myung-bak said the Gulf of Aden was a key shipping route for South Korean cargo vessels as they sail from the Middle East with crude for the world's fifth-largest buyer. "We can no longer leave the lives of this country's people and their assets in danger," Lee said at a ceremony before the ship's departure. "We will protect our safety with our hands." About 460 South Korean vessels pass the gulf every year, local media quoted government sources as saying. South Korean cargo vessels have been captured by Somali pirates in recent years and sailors held hostage for ransom. In February, South Korean sailors were among 23 who were released after being held for three months. Increasingly brazen pirate activity in the Gulf of Aden and Indian Ocean waters off Somalia has driven up insurance costs, forced some ships to go round South Africa instead of through the Suez Canal, and secured millions of dollars in ransoms. Japan on Friday ordered two naval vessels to join the patrols against Somali pirates. Two destroyers will leave a southern port in Japan on Saturday.