has threatened further sanctions and demanded China do more to stop ’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.”
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 In pictures: North Korea military drill
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.”
‘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.