Warships and aircraft from four countries on Thursday staged an exercise off South Korea on preventing the transfer of weapons of mass destruction, Seoul's defence ministry said.
South Korea for the first time is playing a full part in the US-led Proliferation Security Initiative, despite past protests from North Korea that its participation would be seen as a "declaration of war". The South says the drill does not target specific countries.
"The action part of the two-day drill is underway on Thursday," a defence ministry spokesman told AFP. The one-day manoeuvres off the southern port city of Busan came a day after 15 countries held a seminar there to discuss procedures to halt ships suspected of carrying banned weapons.
About 10 ships from South Korea, the United States and Japan -- including a US guided missile destroyer and two Korean destroyers -- were to be involved in Thursday's drill, Yonhap news agency said, quoting military sources. Australia sent P-3C maritime patrol planes and anti-submarine helicopters, the agency said. The ministry spokesman declined to give figures.
South Korea was previously only an observer in the initiative for fear of offending its communist neighbour. After the North's second nuclear test in May last year, it said it would become a full member.
Seoul announced it would host the latest exercise after accusing Pyongyang of torpedoing one of its warships in March and killing 46 sailors. The North denies carrying out the attack.