North Korea test-fired a new anti-aircraft missile Thursday, its official Korean Central News Agency said amid an impasse over nuclear negotiations with the US and frayed ties with South Korea.

The launch is the latest weapons test Pyongyang has conducted since test-firing a hypersonic missile Tuesday and ballistic missiles and a cruise missile earlier in September. It is considered a follow-up on Pyongyang’s plan to bolster its defense capabilities made public at its January congress.

“The Academy of Defense Science test-fired the missile to see its combat performance, along with the functionality of its radar, launcher and battle command vehicle,” the KCNA said on Friday, referring to the North’s weapons developer.

The missile demonstrated remarkable combat performance with its twin rudder control and double impulse flight engine, according to the KCNA.

South Korea’s military said it is “looking into” the missile to verify North Korea’s claims. Experts said the missile was one of the weapons the regime revealed at a military parade in January and last October.

“The twin rudder boosts the missile’s maneuverability and the double impulse flight engine makes the missile fly faster and farther,” said Shin Jong-woo, a senior analyst at the Korea Defense and Security Forum.

Ryu Seong-yeop, an intelligence analyst at the Korea Research Institute for Military Affairs, said the missile is similar to Russia’s S-400 or 500, a surface-to-air missile system. Moscow deployed the latest 500 series in September.

Shin said North Korea was modernizing its weapons system and that South Korea should be prepared to respond to a growing sign of aggression.

On Wednesday, North Korean leader Kim Jong-un said he would reopen the inter-Korean hotlines in early October. The North reached out to the South to reconnect them in July, but since August, Pyongyang has not responded to Seoul’s routine calls because of military drills the South and the US held that month.

Kim said he would also be open to talks if South Korea and the US abandon what he called “double standards,” essentially demanding the two stop condemning his weapons tests, which Pyongyang describes as aimed at bolstering self-defense and not a provocation.

Seoul and Washington, Kim added, should also scrap their “hostile policy,” an accusation he uses to earn relief from sanctions the US and UN have placed over Pyongyang’s nuclear and missile programs.

Cheong Wa Dae has said it will look at the proposal closely. The Unification Ministry, which handles inter-Korean affairs, said it will be ready to have the hotlines up and running and expects to see the calls back on track.

Some experts said Kim’s proposal was a ploy to play Seoul against Washington.

The Moon administration is eager to use any momentum to mend ties and ensure the president’s legacy in inter-Korean affairs, but the US Biden administration is not willing to either condone Kim’s missile tests or use sanctions relief to restart dialogue.

Moon and Kim met three times in 2018 and shook hands on denuclearization, but their meetings have neither brought progress on the agreement nor paved the way for a detente.