North Korea launched two ballistic missiles toward its eastern waters on Thursday, as the United States redeployed one of its aircraft carriers near the Korean Peninsula in response to the North’s recent launch of a powerful missile over Japan.

South Korea’s Joint Chiefs of Staff said in a statement the launches were made 22 minutes apart from the North’s capital region on Thursday morning.

It said South Korea has boosted its surveillance posture and maintains a readiness in close coordination with the United States.

Japanese Prime Minister Fumio Kishida also confirmed the North Korean missile launches, saying the weapons firings are “absolutely intolerable.”

The launches Thursday were North Korea’s sixth round of weapons firings in less than two weeks, which has prompted condemnation from the United States and other countries.

North Korea on Tuesday fired an intermediate-range missile over Japan for the first time in five years, forcing the Japanese government to issue evacuation alerts and halt trains.

It was North Korea’s most provocative weapons demonstration in years. Experts said the weapon was likely a Hwasong-12 missile capable of reaching the U.S. Pacific territory of Guam and beyond.

Thursday’s launches came as the U.S. aircraft carrier USS Ronald Reagan returned to waters east of South Korea in what South Korea’s military called an attempt to demonstrate the allies’ “firm will” to counter North’s continued provocations and threats.

The carrier was in the area last week as part of drills between South Korea and the United States and the allies’ other training involving Japan. North Korea considers such U.S.-led drills near the peninsula as an invasion rehearsal.

The United States and South Korea have also been responding to North Korean tests with their own live-fire drills that have so far involved land-to-land ballistic missiles and precision-guided bombs dropped from fighter jets. But one of the tit-for-tat launches nearly caused catastrophe early Wednesday when a malfunctioning South Korean Hyumoo-2 missile flipped shortly after liftoff and crashed into an air force base in the eastern coastal city of Gangneung. South Korea’s military said no one was hurt from the crash and civilian facilities weren’t affected.

After Tuesday’s launch, the United States, Britain, France, Albania, Norway and Ireland called for an emergency meeting of the U.N. Security Council.

North Korea’s Foreign Ministry said in a statement Thursday that it strongly condemns “the Korean People’s Army on South Korea-U.S. joint drills escalating the military tensions on the Korean Peninsula.”

North Korea carried out a record number of missile tests this year amid long-stalled diplomacy with the United States. Observers say North Korea aims to expand its nuclear arsenal to boost its leverage in future negotiations with the United States.