North Korea slams South Korea-US drills

North Korea's military says recent South Korea-US military exercises were an "open provocation and dangerous war drill", as the South said it had recovered parts of a North Korean missile that landed off its coast.

Last week, North Korea test-fired multiple missiles, including a possible failed intercontinental ballistic missile (ICBM), and hundreds of artillery shells into the sea, as South Korea and the United States carried out six-day air drills that ended on Saturday.

The North's military said the "Vigilant Storm" exercises were an "open provocation aimed at intentionally escalating the tension" and "a dangerous war drill of very high aggressive nature".

The North's army said it had conducted activities simulating attacks on air bases and aircraft, as well as a major South Korean city, to "smash the enemies' persistent war hysteria"

The flurry of missile launches included the most ever in a single day, and come amid a record year of missile testing by the nuclear-armed North Korea.

South Korean and US officials have also said Pyongyang has made technical preparations to test a nuclear device, the first time it will have done so since 2017.

An official at South Korea's Joint Chiefs of Staff said on Monday that a South Korean ship had recovered debris believed to be part of a North Korean short-range ballistic missile (SRBM) that landed off the South's coast last week. It was the first time a North Korean ballistic missile had landed near South Korean waters.

The South Korean Navy rescue vessel used an underwater probe to recover the parts, which are being analysed, the official said.

The North Korean military said it fired two "strategic" cruise missiles on November 2 toward the waters off South Korea's Ulsan, the southeastern coastal city housing a nuclear power plant and large factory parks.

South Korean officials called that claim "untrue" and said they had tracked no missiles near there.

Analysts said some of the photos released by North Korean state media seemed to be recycled from launches earlier in the year.

The operations also included a launch of two "tactical ballistic missiles loaded with dispersion warheads," a test of a "special functional warhead paralysing the operation command system of the enemy," and an "all-out combat sortie" involving 500 fighter jets, according to a statement carried by the official KCNA news agency.

Five hundred fighters would represents almost every dedicated combat aircraft in the North's inventory, which seems unlikely given many are 40 to 80-year-old airframes and not all are serviceable or kept in the active fleet, said Joseph Dempsey, a defence researcher at the International Institute for Strategic Studies.

"(The) 500 figure seems exaggerated or at least misleading," he said in a post on Twitter.

The General Staff of the North's Korean People's Army (KPA) accused Seoul and Washington of eliciting a "more unstable confrontation," and vowed to counter their drills with "sustained, resolute and overwhelming practical military measures."

"The more persistently the enemies' provocative military moves continue, the more thoroughly and mercilessly the KPA will counter them," it said in the statement.