North and South Korea tested ballistic missiles hours apart Wednesday in a display of military might that is sure to exacerbate tensions between the rivals at a time when talks aimed at stripping the North of its nuclear program are stalled.

South Korea’s presidential office said the country conducted its first submarine-launched ballistic missile test. It said the domestically built missile flew from a submarine and hit its designated target while President Moon Jae-in and other top officials looked on.

Moon said improvements in the country’s missile capabilities would serve as “a sure deterrence against North Korean provocation.”

Earlier Wednesday, North Korea fired two short-range ballistic missiles into the sea. Those launches came two days after the North said it fired a newly developed cruise missile, its first weapons test in six months.

Experts say the North Korea is building up its weapons systems to apply pressure on the United States in the hopes of winning relief from sanctions aimed at forcing the North to abandon its nuclear arsenal. US-led talks on the issue have been stalled for more than two years — and in the meantime, tensions have been rising on the Korean Peninsula.

“North Korea is trying to communicate a message that things will not go as Washington wishes, if it doesn’t accept the North’s demands,” said Moon Seong Mook, an analyst with the Seoul-based Korea Research Institute for National Strategy. He said North Korea may think it has an opportunity now to win concessions from US President Joe Biden’s administration while it is embroiled in a domestic debate following the chaotic pullout from Afghanistan.

Meanwhile, observers say Moon’s government, which has been actively pursuing reconciliation with North Korea, may have taken action to appear tougher in response to criticism that it’s too soft on the North.

The rival nations are still technically in a state of war since the 1950-53 Korean War, which pitted the North and ally China against the South and US-led UN forces, ended in an armistice, not a peace treaty.

Japanese Prime Minister Yoshihide Suga said the launches “threaten the peace and safety of Japan and the region and are absolutely outrageous.” The US Indo-Pacific Command said the move “highlights the destabilizing impact of (North Korea’s) illicit weapons program” though it said it didn’t pose an immediate threat to the US.

The South Korean test will likely infuriate the North, which has often accused its rival of hypocrisy for introducing modern weapons while calling for talks between the divided countries.