Theresa May has said China must do more to help end North Korea's "illegal and provocative" weapons testing.

On a visit to Japan, the prime minister welcomed UN condemnation of Pyongyang and said the UK was looking at ways of exerting further pressure on the North Korean regime, including from China.

Mrs May is also aiming to allay Japan's concerns over Brexit and drum up trade.

She said Japanese firms continued to make "important" investments in the UK as EU withdrawal was being negotiated.

She hailed British carmaker Aston Martin's decision to invest £500m in Japan as a sign of the strength of the two countries' economic partnership.

The luxury brand announced on Wednesday it would significantly step up its exports to Japan, open a number of new offices next year and expand its dealer network.

Japan is preoccupied with the issue of North Korea's missile test over its northern Hokkaido island.

Speaking to the BBC after arriving for a three day visit, Mrs May urged China to exert its influence over Pyongyang.

"I want to work with other international partners to do what we all want to do which is to stop North Korea from conducting these illegal activities," she said.

"These are illegal tests. It is outrageous, it is provocative and they should be stopped."

The UK was working to see what "further pressure" could be brought on North Korea, including extending sanctions, and the role that China could play in facilitating such action.

But asked about the comments, a Chinese foreign ministry spokesman said the focus should be on de-escalating tensions in the Korean peninsula and "just chanting about sanctions" was not the answer.

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