- Video report by ITV News China Correspondent Debi Edward
Donald Trump has said "all options are on the table" after North Korea launched a ballistic missile over Japan.
The US president said in a written statement that "threatening and destabilising actions" only increase North Korea's isolation in the region and around the world.
He added that North Korea's actions show "contempt for its neighbours" and that "all option are on the table" for a US response.
However North Korea's ambassador to the United Nations in Geneva, Han Tae Song, said his country will not "flinch an inch" in its development of nuclear weapons as long as "US hostile policies and nuclear threats continue."
The projectile passed over the island of Hokkaido on Tuesday before breaking up into three pieces and landing in the Pacific Ocean, according to officials in Japan.
A spokesman for Seoul's joint chiefs of staff said it was North Korea's 13th launch of ballistic missiles this year.
- International condemnation of latest missile test
UN Secretary General Antonio Guterres has condemned North Korea's latest actions, saying it undermines regional security and stability. He has called on the country to comply fully with its international obligations and "work towards reopening communications channels."
Tokyo criticised Tuesday's launch, labelling it a "grave threat", but insisted the country was prepared to defend itself.
Prime Minister Theresa May criticised the missile test, which she described as "reckless" and "illegal".
The prime minister is heading to the country for talks with counterpart Shinzo Abe amid heightened tensions following Pyongyang's missile launch.
Foreign Secretary Boris Johnson described North Korea's actions as a "reckless provocation".
Meanwhile the foreign ministers of Russia and the United Arab Emirates have both called for North Korea to obey United Nations resolutions.
Earlier this month, the UN Security Council unanimously approved new sanctions on North Korea, which included banning exports worth more than £770 million.
Speaking at a news conference in Abu Dhabi, Sergey Lavrov said "North Korea should respect the United Nations". His Emirati counterpart, Abdullah bin Zayed Al Nahyan, added: "the situation cannot continue to escalate between North Korea on one side and Japan and South Korea on the other."
Elsewhere, French President Emmanuel Macron expressed his support for Japan and said France is ready to do "everything possible ... to bring Pyongyang to the table", although he did not elaborate.
- How has Japan reacted?
Japanese Prime Minister Shinzo Abe said he had a 40-minute phone chat with President Trump following North Korea's latest missile test.
Abe said in a statement: "Japan's and the US positions are totally at one."
Both nations were in "total agreement" that an emergency meeting was needed at the UN Security Council to step up pressures on North Korea after what he called an unprecedented threat.
Earlier, Abe told reporters: "We will do our utmost to protect people's lives."
- What about South Korea?
South Korea's foreign ministry warned that the North will face a "strong response" from the US-South Korean alliance if what it called nuclear and missile provocations continue.
In a rare move, South Korea's military released footage of its own missile tests that were conducted last week.
The videos showed two types of new missiles with ranges of 497 miles and 310 miles being fired from truck-mounted launchers during three tests conducted on Thursday.
- What's the context of the latest missile launch?
South Korean officials said the missile, which travelled around 1,677 miles and reached a maximum height of 341 miles, was launched from Sunan, which is where Pyongyang's international airport is.
It therefore opens the possibility that North Korea launched a road-mobile missile from an airport runway.
The development follows a similar missile exercise carried out by the rogue state on Saturday, where three short-range rockets were fired into the sea off North Korea's coast.
And it comes just weeks after an exchange of threats between North Korea and US president Donald Trump, as tensions over the country' s nuclear ambitions continue to increase.
Analysts speculate the North may have tested a new intermediate-range missile that Pyongyang recently threatened to fire towards the US territory of Guam, which hosts a major military base.
This missile landed nowhere near Guam, which is about 1,550 miles south of Tokyo, but the length of Tuesday's launch may have been designed for the North to show it could follow through on its threat.
North Korea first fired a rocket over Japan in 1998, and carried out a second missile firing over the country in 2009.
Earlier this month, President Trump warned North Korean leader Kim Jong-un he faced "fire and fury" if he continued to pursue his nuclear weapons ambitions.
His comments heightened tensions on the Korean peninsula, already on alert after the North launched its first intercontinental ballistic missile in July - believed to be capable of hitting the US mainland.