Theresa May has threatened further sanctions and demanded China do more to stop North Korea’s nuclear missile launches.

The Prime Minister also would not rule out military force on the Korean Peninsula but said the focus of international action should be intense economic and diplomatic pressure.

She made the comments after deciding to go ahead with a visit to Japan just 36 hours after Pyongyang sent a missile cruising over the north of the country.

The Prime Minister said: “We are very clear that the actions of North Korea are illegal. I think that they are significant actions of provocation.

“I think it is outrageous. That’s why will be working with our international partners, as we have done previously, but we will be re-doubling our efforts with our international partners to put pressure on North Korea to stop these illegal activities.”

She added: “China has a key role to play here in terms of the pressure they can bring on North Korea.”

Later she told her Japanese counterpart Shinzo Abe that Britain stood “shoulder to shoulder” with Japan.

Her visit focussing on trade and security went ahead despite the launch of a missile over the northern Japanese island of Hokkaido, which then broke up and landed in the Pacific Ocean.

In pictures: North Korea military drill Show all 8 1 /8 In pictures: North Korea military drill In pictures: North Korea military drill North Korea's leader Kim Jong Un watches a military drill marking the 85th anniversary of the establishment of the Korean People's Army (KPA) KCNA/Handout via REUTERS In pictures: North Korea military drill A military drill marking the 85th anniversary of the establishment of the Korean People's Army (KPA) is seen in this handout photo by North Korea's Korean Central News Agency (KCNA) KCNA/Handout via REUTERS In pictures: North Korea military drill A military drill marking the 85th anniversary of the establishment of the Korean People's Army (KPA) is seen in this handout photo by North Korea's Korean Central News Agency (KCNA) KCNA/Handout via REUTERS In pictures: North Korea military drill A military drill marking the 85th anniversary of the establishment of the Korean People's Army (KPA) KCNA/Handout via REUTERS In pictures: North Korea military drill A military drill marking the 85th anniversary of the establishment of the Korean People's Army (KPA) KCNA/Handout via REUTERS In pictures: North Korea military drill This image made from video of still images broadcast in a news bulletin by North Korea's KRT, shows what was said to be a 'Combined Fire Demonstration' held to celebrate the 85th anniversary of the North Korean army, in Wonsan, North Korea. KRT via AP Video In pictures: North Korea military drill This image made from video of still images broadcast in a news bulletin by North Korea's KRT, shows what was said to be a 'Combined Fire Demonstration' held to celebrate the 85th anniversary of the North Korean army, in Wonsan, North Korea. KRT via AP Video In pictures: North Korea military drill This image made from video of still images broadcast in a news bulletin by North Korea's KRT, shows what was said to be a 'Combined Fire Demonstration' held to celebrate the 85th anniversary of the North Korean army, in Wonsan, North Korea. KRT via AP Video

The Prime Minister refused to rule out future British military action against North Korea or cyber warfare after being quizzed by reporters four times on the issue.

Ms May said: “I think what I have made clear is what the UK is looking at and what the UK doing and that is looking at pressure on North Korea, which is discussions about further sanctions and it’s about the sort of change that China can bring. I think they are a key player in this.”

“We would encourage China to do everything it can to bring pressure on North Korea to stop this.”

But Beijing went on the offensive, with foreign ministry spokeswoman Hua Chunying claiming critics “only pay attention to sanctions and pressure, and ignore peace talks”.

She added: “You will reap what you sow. The parties directly concerned should take responsibility.”

Kim Jong-un‘s nuclear and ballistic missile programmes were already on the agenda for the three-day visit, which begins in Kyoto.

Ms May will attend a meeting of the Japanese National Security Council on Thursday, with former Australian premier Tony Abbott the only other foreign leader to have been given the honour.

The UN also condemned North Korea’s “outrageous” firing of a ballistic missile over Japan in a US-drafted statement, which demanded that the isolated country halt its weapons programme.

For its part, North Korea said the launch of the intermediate-range ballistic missile (IRBM) was in response to US and South Korean military drills.

Mr Kim ordered the launch as a first step in military action in the Pacific to “contain” the US territory of Guam, according to a statement run by the KCNA news agency on Wednesday.

More exercises would be needed, Mr Kim said. “The current ballistic rocket launching drill like a real war is the first step of the military operation of the KPA in the Pacific and a meaningful prelude to containing Guam,” KCNA quoted Mr Kim as saying. KPA stands for the Korean People’s Army.

Earlier this month North Korea threatened to fire four missiles into the sea near Guam, home to a major US military presence base, after President Donald Trump said the North would face “fire and fury” if it threatened American territory.

Also on Wednesday, the US military announced it had completed a “complex” test flight involving the interception of a missile in mid-air.

The 15-member UN Security Council said it was of “vital importance” that North Korea take immediate, concrete actions to reduce tension and called on all other UN member states to implement sanctions.

The statement, which was agreed by consensus, did not threaten new sanctions on North Korea.