South Korean warships joined three US aircraft carriers Saturday in an unusually strong display of naval force aimed at North Korea, whose nuclear ambitions have been a focus of US President Donald Trump's ongoing tour of Asia.
The four-day joint exercise in the western Pacific involves three flattops -- USS Ronald Reagan, USS Nimitz and USS Theodore Roosevelt -- and seven South Korean warships including three destroyers, Seoul's defence ministry said.
It is the first such triple-carrier drill in the region for a decade.
"The exercise is aimed at enhancing deterrence against North Korea's nuclear and missile threats and showing off preparedness to fend off any provocative acts by the North," a ministry spokesman said.
Nuclear-armed North Korea regularly denounces such military drills as rehearsals for invasion and sometimes conducts its own military manoeuvres or missile tests in response.
The US warships will carry out air defence drills, sea surveillance, defensive air combat training and other training operations, the US Navy said.
The exercises come on the heels of Trump's visits to Seoul and Beijing this week, which were dominated by the question of how to counter Pyongyang's nuclear weapons threat.
In a speech to the South Korean parliament on Wednesday, Trump warned North Korea not to underestimate the United States, while offering leader Kim Jong-Un a better future if he gives up his nuclear ambitions.