North Korea has fired four ballistic missiles, angering its neighbors and sparking condemnation from countries including China, its only major supporter and trade partner.
The missiles launched in the morning on March 6 flew about 1,000 kilometers on average, three of them landing in waters that Japan claims as its exclusive economic zone, South Korean and Japanese officials said.
Japanese Prime Minister Shinzo Abe called it "an extremely dangerous action" and said that "strong protests" had been lodged with Pyongyang.
Repeated missile launches by North Korea "clearly violate UN Security Council resolutions," Abe said. "We can never tolerate this."
On March 3, North Korea threatened to fire missiles in response to the Foal Eagle military exercises under way between South Korea and the United States.
The annual drills infuriate North Korea, which says it sees them as preparation for potential aggression. Seoul and Washington call the military drills defensive and routine.
The Chinese Foreign Ministry said that Beijing "opposes North Korea's violation of the UN Security Council's stipulation" -- a reference to multiple council resolutions calling on Pyongyang to refrain from ballistic missile tests.
However, China also suggested that South Korea and the United States were partly to blame.
"Under current circumstances, relevant parties should exercise restraint and avoid anything that would provoke each other or heighten regional tensions," Foreign Ministry spokesman Geng Shuang said.
Geng said that China's top envoy on North Korea nuclear issues, We Dawei, had called his counterparts in Washington and Seoul on March 3.
Wu warned both Washington and Seoul that the joint military exercise "may widen divisions" and further complicate the situation on the Korean peninsula, the spokesman said.
Moscow 'Seriously Worried'
In Moscow, Kremlin spokesman Dmitry Peskov said Russia is "seriously worried" over the latest missile launch by North Korea.
"These are the sort of actions that lead to a rise in tension in the region and of course in this situation, traditionally, Moscow calls for restraint from all sides," Peskov told reporters.
According to South Korea's military, the ballistic missiles were fired from the Tongchang-ri region, near North Korea's border with China.
South Korea's Acting President and Prime Minister Hwang Kyo Ahn called a meeting of the UN Security Council.
The UN Security Council, whose permanent members are the United States, Russia, China, Britain, and France, has adopted several resolutions since 2006 that impose and strengthen sanctions on North Korea for continuing to develop its nuclear weapons program.
The resolutions call on Pyongyang to dismantle its nuclear program "in a complete, verifiable, and irreversible manner" and refrain from ballistic missile tests.
Nuclear-armed North Korea has test-launched a series of missiles of various ranges in recent months. It also conducted two nuclear tests last year.
The United States withdrew nuclear weapons from South Korea in 1991 before Seoul and Pyongyang signed a declaration on the denuclearization of the Korean peninsula.
Pyongyang has since walked away from the agreement, citing what it says is the threat of invasion by the United States.
The United States has 28,500 troops stationed in South Korea, and 50,000 in Japan, as a deterrent against a potential aggression from the North.
The Korean Peninsula remains in a technical state of war because the 1950-53 Korean War ended with an armistice and not a peace treaty.
With reporting by AP, AFP, Reuters, Interfax, and dpa