North Korea test-fired multiple short-range ballistic missiles on Sunday, South Korea's military said, the latest in a recent flurry of launches by the nuclear-armed state.

The Sunday launches add to a series of weapons tests Pyongyang has carried out in recent weeks, including ballistic missiles, anti-warship cruise missiles and cluster munitions.

"Our military detected several short-range ballistic missiles fired into the East Sea from the Sinpo area of North Korea at around 6:10 am (2110 GMT)," South Korea's Joint Chiefs of Staff said, referring to a body of water also known as the Sea of Japan.

"The missiles flew approximately 140 kilometres (87 miles), and South Korean and US intelligence authorities are conducting a detailed analysis of their exact specifications," it added.

Seoul was maintaining a "firm combined defence posture" with its security ally the United States, which stations about 28,000 troops in the South to help it defend against military threats from the North, and will "respond overwhelmingly to any provocation", it said.

South Korea's presidential office said it held an emergency security meeting over the launches.

Analysts said the tests signalled Pyongyang's latest rejection of attempts by Seoul to repair strained ties.

Among them was an expression of regret from Seoul over civilian drone incursions into the North in January, a gesture initially described as "very fortunate and wise behaviour" by Kim Yo Jong, the powerful sister of the North Korean leader.

But this month, a senior North Korean official described the South as "the enemy state most hostile" to Pyongyang, reviving a label previously used by leader Kim Jong Un.

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.

"Pyongyang must immediately halt its successive missile provocations that are heightening tensions," Seoul's defence ministry said in a statement.

The North should "actively engage in the South Korean government's efforts to establish peace", it added.

Two more destroyers

Earlier in April, Kim Jong Un oversaw tests of strategic cruise missiles launched from a naval warship, with official photos showing him watching the firings flanked by military officials.

Those tests were carried out from the Choe Hyon, one of two 5,000-ton destroyers in the North's arsenal, both launched last year as Kim Jong Un seeks to ramp up the country's naval capabilities.

The North is also building two more 5,000-ton class destroyers to add to its fleet.

A South Korean lawmaker said this month that North Korea appeared to be speeding up construction of a destroyer at the western port city of Nampo.

Citing satellite imagery from a US-based intelligence firm, Yoo Yong-won of the opposition People Power Party said North Korea was "accelerating the naval forces' modernisation on the back of military assistance from Russia".

North Korea has sent ground troops and artillery shells to support Russia's invasion of Ukraine, and observers say Pyongyang is receiving military technology assistance from Moscow in return.