Analysts have said that by conducting a series of missile tests in recent months, Pyongyang may be trying to take advantage of eroding international norms to cement its nuclear status.

The diplomatically isolated North has also repeatedly shunned efforts by the South Korean government to improve relations, calling Seoul its most "hostile" adversary.

South Korea's Joint Chiefs of Staff said they had detected the launches of "several projectiles" at around 1:00 pm (0400 GMT) from the North Korean city of Chongju into the Yellow Sea, the body of water separating the Korean peninsula from China.

The launches included a short-range ballistic missile, Seoul's military said.

The missiles flew about 80 kilometres (50 miles), the military said, adding that it was analysing their specifications and flight range, and had "strengthened surveillance and vigilance in preparation for possible additional launches".

Seoul's foreign ministry spokesperson Park Il said at a regular news briefing that the government once again urges North Korea to respond to their peace policy and efforts to ease tensions.

"As we firmly support nuclear non-proliferation, we will continue our efforts to achieve substantive progress in resolving the North Korean nuclear issue through a step-by-step and pragmatic approach, while adhering to the goal of complete denuclearisation," he said.

North Korea is subject to multiple United Nations sanctions banning its nuclear weapons development and use of ballistic missile technology, restrictions it has repeatedly flouted.

South Korea, along with its main security partner the United States and Japan, were "maintaining a state of full readiness" and closely sharing intelligence, Seoul's military said.

Tuesday's launches were North Korea's first in 37 days and its eighth test this year.

In April, Pyongyang conducted a ballistic missile test to "verify the characteristics and power of a cluster bomb warhead", its state media said at the time.

South Korea's Yonhap news agency reported last week, citing unnamed government sources, that Chinese President Xi Jinping would likely visit North Korea this week.

China is North Korea's main economic and political backer, though Pyongyang has drawn closer to Russia in recent years.

Neither Beijing nor Pyongyang have confirmed Xi's visit.