North Korea test-fired two ballistic missiles capable of striking Japan on Sunday, in a possible protest at Tokyo’s adoption of a new security strategy to push for a more offensive stance against North Korea and China.

The launches also came two days after the North claimed to have performed a key test needed to build a more mobile, powerful intercontinental ballistic missile designed to strike the US mainland.

The two missiles travelled from the country’s northwest Tongchangri area about 310 miles at a maximum altitude of 340 miles before landing in the waters between the Korean Peninsula and Japan, according to the South Korean and Japanese governments.

South Korea’s military said both missiles were launched at a steep angle, suggesting the weapon could have travelled farther if fired at a standard trajectory.

North Korea usually tests medium and longer-range missiles at a high angle to avoid neighbouring countries, though it fired an intermediate-range missile over Japan in October, forcing Tokyo to issue evacuation alerts and halt trains.

In an emergency meeting, top South Korean security officials attacked North Korea’s continued provocations that they said came despite “the plight of its citizens moaning in hunger and cold due to a serious food shortage”.

They said South Korea will boost a trilateral security co-operation with the US and Japan, according to South Korea’s presidential office.

Japanese vice defence minister Toshiro Ino separately criticised North Korea for threatening the safety of Japan, the region and the international community.

The US Indo-Pacific Command said the launches highlight the destabilising impact of North Korea’s unlawful weapons of mass destruction and ballistic missile programmes.

It said the US commitments to the defence of South Korea and Japan “remain ironclad”.

Kwon Yong Soo, a former professor at Korea National Defence University in South Korea, said North Korea probably tested its Pukguksong-2 missile, a solid-fuelled, land-based variant of its Pukguksong family of missiles that can be fired from submarines.

Kwon said the Pukguksong-2 can fly about 745 to 1,240 miles if it is launched at a normal trajectory, a range enough to strike key facilities in Japan, including US military installations there. Some experts say the Pukguksong-2 is nuclear-capable.

On Friday, the Japanese government adopted a national security strategy that would allow it to carry out pre-emptive strikes and fire powerful cruise missiles to give itself more offensive footing against threats from neighbouring China and North Korea.

That was a major break from its strictly self-defence-only post-war principle.

The Japanese strategy names China as “the biggest strategic challenge” – before North Korea and Russia – to Japan’s efforts to ensure peace, safety and stability for itself and the international community.

Sunday’s launch is the North’s first public weapons test since it launched last month its developmental, longest-range liquid-fuelled Hwasong-17 ICBM capable of reaching the entire US homeland.

Earlier this year, North Korea test-launched a variety of other missiles at a record pace.

North Korea has defended its weapons testing as self-defence measures to cope with the expanded US-South Korea military drills that it views as an invasion rehearsal.

But some experts say North Korea likely used its rivals’ military training as an excuse to enlarge its arsenal and increase leverage in future negotiations with the US to win sanctions relief and other concessions.