North Korea has fired another intermediate-range missile over Japan and into the Pacific Ocean.
This is the second such test in recent weeks.
The missile reportedly travelled about 3,700 kilometres (2,300 miles) and reached a maximum height of 770 kilometres (478 miles) before landing in waters just off Japan.
In response, South Korea fired two ballistic missiles into the sea in a simulated strike on North Korea, minutes after the North's launch.
South Korea's president Moon Jae-in has instructed his officials to pursue "stern" diplomatic and military measures to discourage North Korea from further provocations.
The US secretary of state, Rex Tillerson, has since called for the world to take "new measures" against North Korea’s aggressive actions.
In his statement, he singled out Russia and China as nations who had particular strategic power to apply pressure on the North Korean regime.
North Korea has carried out a series of nuclear provocations in recent months; following US President Donald Trump's threats of "fire and fury", Pyongyang has conducted a test of its most powerful weapon yet and fired two missiles close to Japan.
The test increases already heightened fears that North Korea will be in possession of a missile capable of reaching the US mainland.
North Korea has vowed to continue its nuclear tests amid what it perceives to be American hostility.
The missile was launched from Sunan, Pyongyang's international airport - the same origin as the earlier missile that flew over Japan.
Analysts have speculated the new test was of the same intermediate-range missile launched in that earlier flight, the Hwasong-12.
Foreign Secretary Boris Johnson said: "North Korea has conducted yet another illegal missile launch.
"The UK and the international community have condemned the aggressive and illegal actions of the North Korean regime, and the succession of missile and nuclear tests.
"We stand firmly by Japan and our other international partners."
"This week the most stringent UN sanctions regime placed on any nation in the 21st century was imposed on North Korea, after being unanimously agreed at the UN Security Council.
"These measures now need to be robustly enforced. We urge all states to play their part in changing the course North Korea is taking."
Japanese Prime Minister Shinzo Abe and US Defence Secretary Jim Mattis also called the launch a reckless act.
The UN Security Council scheduled an emergency closed-door meeting to be held on Friday afternoon in New York.
North Korea claimed its latest nuclear test was a detonation of a thermonuclear weapon built for its intercontinental ballistic missiles, which could potentially reach deep into the US mainland when perfected.
The UN Security Council unanimously approved new sanctions earlier this week over the nuclear test.
It has banned all textile exports and prohibited any country from authorising new work permits for North Korean workers - two key sources of hard currency.
It's also blocked North Korea from importing all natural gas liquids and condensates, and capped Pyongyang's imports of crude oil and refined petroleum products.