Foreign Secretary William Hague has said Britain must "keep calm" as he played down fears of an escalation of violence from a "provocative" North Korea, while confirming embassy officials will not be leaving Pyongyang.
Mr Hague told Daybreak "we should be worried that North Korea is developing nuclear weapons (and) missiles" but said, as a country, we must remain "firm, united and calm" in the face of the growing war "rhetoric".
"North Korea wants to show that it is a victim and to create a sense of crisis, so we shouldn't play to that all of the time," he said.
Tour companies in China say they have been instructed to suspend trips into North Korea after the war rhetoric coming out of Pyongyang stoked up war tensions in the region.
Chinese authorities in the northeastern city of Dandong, which borders North Korea, have told at least five tour agencies to halt overland tourism into the country.
"All (tourist) travel to North Korea has been stopped from today, and I've no idea when it will restart," a travel agent told Reuters.
The border remains open to commercial traffic though.
An initial South Korean investigation has found North Korea responsible for a cyberattack in March, the Associated Press reports.
The Japanese government has said it is "on high alert" and was preparing for a possible North Korean missile launch that could threaten Japan as well as its US and South Korean allies.
Missile interceptors have been deployed in key locations around Tokyo as a precaution.
Japanese Prime Minister Shinzo Abe told reporters that they would take every possible measure to protect their citizens.
On Tuesday, North Korea urged foreign companies and tourists to leave South Korea as the situation on the Korean Peninsula was "inching close to a thermonuclear war."
South Korean lawmakers have urge Pyongyang to resume operations in Kaesong joint industrial park where it has pulled out workers for a second day.
The Democratic United Party's Choo Mi-Ae said: "It's not too late. The North Korean government should stop all provocative behaviour and change its course toward peace and stability on the Korean peninsular.
There is speculation that North Korea could launch a missile today - perhaps aimed at Japan.
Talking to senior diplomats there is a sense is that if the missile trajectory shows it will land harmlessly in sea then it won't be shot down
UN Secretary General Ban Ki-moon has warned that the tensions between North and South Korea could become “uncontrollable”.
He said: "The current level of tension is very dangerous. A small incident caused by miscalculation or misjudgment may create an uncontrollable situation."
Speaking in Rome, he said he had urged North Korean authorities to refrain from "provocative rhetoric" and asked neighbouring countries to try to exert their influence on Pyongyang.
Anders Fogh Rasmussen, the secretary general of NATO, will travel to South Korea this week as tensions with the North continue to rise.
He will arrive Thursday and hold a series of meetings with South Korean president Park Geun-hye, foreign minister Yun Byung-se and defence minister Kim Kwan-jin, reports Yonhap news agency.
It is the first time a NATO chief visits the country.
Meanwhile, the office of Park Geun-hye has described a warning by the North – that foreigners in South Korea should evacuate in case war breaks out – as "psychological warfare", according to Bloomberg.