Sharjah 24 – AFP: North Korea fired four ballistic missiles on Saturday, the South Korean military said, the latest in Pyongyang's testing blitz this week as Washington and Seoul concluded their biggest-ever air force drills.

The flurry of North Korean launches included an intercontinental ballistic missile and one that landed near the South's territorial waters. South Korean President Yoon Suk-yeol said it was "effectively a territorial invasion".

The launches came as hundreds of US and South Korean warplanes -- including B-1B heavy bombers -- participated in the Vigilant Storm exercise, which Pyongyang described as "aggressive and provocative".

"The South Korean military detected four short-range ballistic missiles launched by North Korea from Tongrim, North Pyongan Province, to the West Sea at around 11:32 a.m. to 11:59 a.m. today," South Korea's Joint Chiefs of Staff (JCS) said in a statement on Saturday, using another name for the Yellow Sea.

Their "flight distance was detected at about 130 km (80 miles), an altitude of about 20 km, and a speed of about Mach 5", they added. Mach 5 is equivalent to five times the speed of sound.

The United States and South Korea have warned that these launches could culminate in a nuclear test by North Korea, and extended their air force drills to Saturday in response.

Vigilant Storm was originally scheduled to run from Monday to Friday.

Pyongyang ramped up missile launches in response to the drills. Such exercises have long provoked strong reactions from North Korea, which sees them as rehearsals for an invasion.

Vigilant Storm concluded on Saturday, with the US Air Force deploying two B-1B long-range heavy bombers on the final day in a ramped-up show of force.