North Korea has said its latest missile launch was a warning to South Korean "warmongers" to stop importing weapons and conducting joint military drills, a message that analysts said was also aimed at the United States.

North Korean leader Kim Jong Un personally watched the test-fire of two short-range ballistic missiles yesterday, the first test since Mr Kim met with US President Donald Trump last month and agreed to revive denuclearisation talks.

The missile tests raises doubts about the revival of denuclearisation talks, which stalled after the collapse of a second summit between Mr Kim and Mr Trump in Hanoi in February.

"We cannot but develop nonstop super-powerful weapon systems to remove the potential and direct threats to the security ofour country that exist in the south," Mr Kim said, according to state news agency KCNA.

An official at Seoul's defence ministry said the missiles were believed to be a new type of short-range ballistic missile, an assessment echoed on Friday by the US-South Korea Combined Forces Command.

A joint review with the United States showed that both missiles flew some 600 km, further than similar previous missile tests, the defence official told Reuters.

The official also said the missiles bore features similar to Russia' SS-26 Iskander and the ones the North tested in May – a relatively small, fast missile that experts say is easier to hide, launch and manoeuvre in flight.

A spokesman for the CFC said in a statement the launches were "not a threat directed at [South Korea] or the US, and have no impact on our defence posture."

North Korea has shown increasing frustration via state media that South Korea has not followed through on promised economic co-operation or peace agreements, all while importing the latestF-35 stealth fighters and conducting military drills with the US.

The KCNA report did not mention Mr Trump or the United States, but said Mr Kim criticised South Korean authorities for staging joint military exercises, which Mr Trump promised to end after his first meeting with Mr Kim in June 2018.

North Korea accused the US of breaking that promise by planning to hold joint military exercises with South Korea next month and warned of a possible end to its freeze in nuclear and long-range missile tests.

While the latest message is very clearly directed at Seoul, it does send signals to the US as well, said Jenny Town, managing editor at 38 North, a project that studies North Korea.

"On some level, this is like North Korea's version of maximum pressure on South Korea and the United States."