North Korea launches more missiles as Kim sister warns Pacific could become ‘firing range’

North Korea fired two ballistic missiles off its east coast Monday, South Korea’s military said, as the powerful sister of the North’s leader, Kim Jong-un, warned the nuclear-armed state could turn the Pacific into a “firing range”.

The tests prompted the head of the ruling party in South Korea to warn that continued provocations by Pyongyang would only strengthen calls for the South to develop its own nuclear deterrent – a move that would dramatically raise tensions on the peninsula.

The launches come just two days after North Korea fired an intercontinental ballistic missile (ICBM) into the sea off Japan’s west coast, prompting joint air exercises by the US and South Korea on Sunday.

Kim Jong-un’’s sister, Kim Yo-jong, warned against the increased presence of US strategic assets on the Korean peninsula after the US held joint air exercises with South Korea and separately with Japan on Sunday.

“We are carefully examining the influence it would exert on the security of our state,” she said in a statement reported by state media “The frequency of using the Pacific as our firing range depends upon the US forces’ action character.”

Chung Jin-suk, head of the ruling People Power party, said South Korea had a “clear option” to counter the North’s continued development of ballistic missiles and nuclear weapons.

“We must first secure a concrete nuclear deterrence,” Chung told a party meeting, according to the Yonhap news agency. “We need to strengthen our ‘Kill Chain’ so North Korea can never rise to its feet again if it uses nukes on the Korean peninsula.”

Kill Chain refers to a preemptive strike capability under which the South, facing an imminent nuclear attack from the North, would attempt to “decapitate” the regime’s leadership.

Chung added: “We need to seriously consider developing our own nuclear capabilities if such a response is insufficient.”

There is strong public support for the idea of arming South Korea with nuclear weapons, as concern grows over North Korea’s development of weapons of mass destruction. A Gallup Korea poll last month showed that 76% of respondents said the country needs to develop its own nuclear deterrent – three times as many as opposed the idea.

North Korea’s state media confirmed on Monday the country had fired two projectiles from a multiple rocket launcher, aiming at targets 395km (245 miles) and 337km (209 miles) away.

“The 600mm multiple rocket launcher mobilised in the firing … is a means of tactical nuclear weapon” capable of “paralysing” an enemy airfield, state news agency KCNA reported.

Japan’s defence ministry said the two ballistic missiles fired on Monday morning reached a maximum altitude of about 100km and 50km, travelling a distance of about 350-400km before falling outside Japan’s exclusive economic zone.

“North Korea’s series of actions, including its repeated ballistic missile launches, threaten the peace and security of Japan, the region, and the international community,” the ministry said. “Japan lodged a strong protest and forcefully condemned North Korea.”

In a statement, the ministry said it would continue to gather and analyse information in close cooperation with the US.

There were no reports of damage to aircraft or vessels.

US Indo-Pacific Command said: “While we have assessed that this event does not pose an immediate threat to US personnel or territory, or to our allies, the missile launches highlight the destabilising impact of [North Korea’s] unlawful WMD and ballistic missile programmes. The US commitments to the defence of the Republic of Korea and Japan remain ironclad.”

UN secretary general Antonio Guterres condemned the North’s earlier launch of an intercontinental ballistic missile and called on Pyongyang to cease “provocative actions”, his spokesman said on Sunday.

“The secretary general strongly condemns the launch of yet another ballistic missile of intercontinental range by the Democratic People’s Republic of Korea,” spokesman Stephane Dujarric said, using the country’s official name. He added that Guterres reiterated a call for Pyongyang “to immediately desist from taking any further provocative actions”.

Kim Yo-jong also rejected comments by some South Korean experts who questioned whether North Korea’s ICBMs would be functional in real-war situations. Their assessment pointed out that it took over nine hours for the “sudden” missile launch to take place following an order from Kim Jong-un.

“We have possessed satisfactory technology and capability and, now will focus on increasing the quantity of their force,” she said.

Monday’s missile launch is the North’s third major weapons test this year, and comes after Pyongyang threatened an “unprecedentedly persistent, strong” response as South Korea and the US prepared to begin annual military exercises that the North regards as a rehearsal for an invasion.