North Korea fired what appeared to be several land-to-ship missiles off its east coast on Thursday, South Korea's military said, the latest in a fast-paced series of missile tests defying world pressure to rein in its weapons program.

The launches come less than a week after the United Nations Security Council passed fresh sanctions on the reclusive state, which said it would continued to pursue its nuclear and missile program without delay.

The warship-killing cruise missiles were launched Thursday morning from the North Korean coastal city of Wonsan and flew about 200km, South Korea's Office of Joint Chiefs of Staff said in a statement.

South Korean President Moon Jae-in has been briefed on the latest launch, the military said, declining to give further details.

"North Korea launched multiple projectiles that appear to be short-range land-to-ship cruise missiles today morning off east coast from the region of Wonsan," the office said in a statement, adding that Seoul and Washington were analysing the launches for further information.

Thursday's launch is the fourth missile test by North Korea since Moon took office on May 10 pledging to engage in dialogue with Pyongyang, saying sanctions and pressure alone have failed to resolve the growing threat from the North's advancing nuclear and missile program.

South Korea said on Wednesday it will hold off on installing remaining components of a controversial US anti-missile defense system until it completes an assessment of the system's impact on the environment.

Under third-generation leader Kim Jong-un, North Korea has been conducting such tests at an unprecedented pace in an effort to develop an intercontinental ballistic missile (ICBM) capable of hitting the mainland United States.

In the three earlier launches, North Korea tested different kinds of ballistic missiles, two medium-to-long range missiles as well as a short-range Scud class weapon.

The launches of the apparent anti-ship missiles on Thursday follow Kim's order to develop North Korea's own ballistic missile that precisely strikes targets such as enemy vessels, reported in its state media late last month.

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 program is necessary to counter US aggression.