South Korean and US troops have begun five days of naval drills amid North Korea's renewal of its threat to fire missiles near the American territory of Guam.
South Korea's navy says the drills that began on Monday in the waters off the Korean Peninsula involve fighter jets, helicopters as well as 40 naval ships including the aircraft carrier USS Ronald Reagan.
South Korean and US militaries regularly conduct joint exercises, though North Korea condemns them as an invasion rehearsal.
North Korea last week accused the United States of provoking the country by mobilising the aircraft carrier and other war assets near the peninsula.
The North said it could take military counteraction such as a salvo of missile launches into waters near Guam.