North Korea fired two suspected cruise missiles Tuesday, Seoul said, its fifth weapons test this year as Pyongyang flexes its military muscles while ignoring US offers of talks.

The last time North Korea tested this many weapons in a month was in 2019, after high-profile negotiations collapsed between leader Kim Jong Un and then-US president Donald Trump.

This year Pyongyang has embarked on a fresh flurry of sanctions-busting tests, including hypersonic missiles, after Kim re-avowed his commitment to military modernisation at a key party speech in December.

Washington imposed new sanctions in response, prompting Pyongyang to double down on weapons testing and hint last week that it could abandon a years-long self-imposed moratorium on nuclear and long-range tests.

"North Korea fired two suspected cruise missiles," South Korea's Joint Chiefs of Staff said in a statement Tuesday, without giving further details.

Cruise missiles are not banned under current UN sanctions on North Korea, and Seoul does not always report such launches in real time, as it does for ballistic missile tests.

The last time North Korea is known to have tested a cruise missile was in September 2021.

A South Korean military official told the Yonhap news agency that "should such a missile be launched southward, our detection and interception systems have no problem countering it".

Pyongyang's latest test looks like an attempt to provoke the administration of US President Joe Biden, which has offered talks "without preconditions" but no substantive high-level engagement in the last year.

People watch a television in Seoul showing a news broadcast with file footage of a North Korean missile test People watch a television in Seoul showing a news broadcast with file footage of a North Korean missile test Photo: AFP / Jung Yeon-je

"North Korea appears to be wanting to test Washington's reaction, while showing off its presence on the global stage," Yang Moo-jin, a professor at the University of North Korean Studies, told AFP.

By firing a cruise missile, Pyongyang does not violate UN sanctions but can still try "to attract the world's attention while thumbing its nose at the US".

The string of launches in 2022 comes at a delicate time in the region, with Kim's sole major ally China set to host the Winter Olympics next month and South Korea gearing up for a presidential election in March.

Domestically, North Korea is preparing to celebrate the 80th anniversary of the birth of late leader Kim Jong Il in February, as well as the 110th birthday of founder Kim Il Sung in April.

Pyongyang has not tested inter-continental ballistic missiles or nukes since 2017, putting launches on hold as Kim embarked on a blitz of high-level diplomacy through three meetings with Trump.

But last week Pyongyang said it could examine restarting all temporarily-suspended activities.

The impoverished North, reeling economically from a self-imposed coronavirus blockade, has recently restarted cross-border trade with China.

And ally Beijing, along with Russia, last week blocked the UN Security Council from imposing fresh sanctions in response to the recent tests.

Defector-turned-researcher Ahn Chan-il told AFP the tests could also be an attempt by Pyongyang to pressure China.

"The Beijing Olympics cannot be a festival of peace without peace on the Korean Peninsula," he said.

"And peace on the Korean Peninsula depends on North Korea."