North Korea fired what appeared to be several land-to-ship missiles off its east coast on Thursday, South Korea's military said.

The development surfaced a day after South Korea postponed full deployment of a controversial US anti-missile system designed to deter a North Korean attack. The launches come less than a week after the United Nations Security Council passed fresh sanctions on the reclusive state.

The projectiles were fired Thursday from the North Korean eastern coastal town of Wonsan and likely flew about 200 kilometres, South Korea's Joint Chiefs of Staff said. They landed in waters between the Korean Peninsula and Japan, where US aircraft carriers USS Carl Vinson and USS Ronald Reagan participated in joint exercises with the South Korean navy that ended earlier this week.

North Korea has been conducting missile tests at an unprecedented pace in an effort to develop an intercontinental ballistic missile (ICBM) capable of hitting the mainland United States.

Compared to the different types of ballistic missiles Pyongyang has recently tested, the missiles launched on Thursday are considered to be more defensive in nature, designed to defend against threats such as enemy warships.

North Korea unveiled a number of new weapons at a massive military parade on April 15 to mark the birth anniversary of the state's founding leader and has since tested some of them.

“What appeared to be a new type of land-to-ship missile equipped with four launching canisters was unveiled at the parade,” said Kim Dong-yub, a military expert at Kyungnam Universitys Far Eastern Studies in Seoul.

“I think this might be what was used today.”

THAAD defence delayed

South Korea on Wednesday said it will hold off on installing remaining components of the US Terminal High Altitude Area Defence (THAAD) system that has angered North Korea's main ally, China, amid early signs of easing tensions between the two countries.

Thursday's launch is the fourth missile test by North Korea since South Korean President Moon Jae-in took office on May 10 pledging to engage in dialogue with Pyongyang. Moon says sanctions and pressure alone have failed to resolve the growing threat from the North's advancing nuclear and missile programme.

Moon had also promised to review the deployment of the THAAD system in South Korea, a decision that was made by the government of his conservative predecessor, Park Geun-hye.

On Wednesday, Moon's office said installation of four additional launchers would be halted until an assessment of the system's impact on the environment was completed.

Two launchers of the full six-launcher THAAD battery, as well as the system's far-reaching radar that China worries could upset the regional security balance, have already been installed at a deployment site in the southeastern city of Seongju. The elements will stay in place, South Korea said.

The introduction of the THAAD system has sparked protests in South Korea and a backlash in China against South Korean business interests.

The Global Times, published by China's official People's Daily, said in an editorial that no matter the outcome of the environmental study, South Korea's announcement could reduce friction.

“Obviously, the pressure China puts on South Korea has taken effect. Seoul's will has been shaken,” the paper said.

There was no immediate official reaction from China to the latest missile test.

US President Donald Trump has been pressing China aggressively to rein in North Korea, warning that all options, including a preemptive military strike, are on the table if Pyongyang persists with its nuclear and missile development.

Seoul, Tokyo and Washington were analysing the launches for further information, officials said. “North Korea likely wanted to show off its ability to precisely target a large warship, in relation to the joint military drills involving US aircraft carriers,” Roh Jae-cheon, South Korea's Joint Chiefs of Staff spokesman, told a media briefing.

“By testing different types of missiles, North Korea also appears to be aiming to secure the upper hand in relations with South Korea and the United States.”

The isolated country, which has conducted dozens of missile tests and tested two nuclear bombs since the beginning of 2016 in defiance of UN Security Council resolutions, says the programme is necessary to counter US aggression.

South Korea leader warns North after missile launch

South Korean President Moon Jae-in said during a National Security Council meeting he “won't back off even a single step and make any compromise” on the issue of national security. He warned that North Korea could only face further international isolation and more economic difficulties.

In what will likely become another source of animosities, Moon's government said Thursday that it will let two of the four North Korean fishermen recently rescued at sea resettle in the South in accordance with their wishes.

The two other fishermen who want to return home will be repatriated. Pyongyang is expected to demand the return of all four fishermen by accusing Seoul of enticing them to defect to the South.