North Korea fired what appears to be two short-range ballistic missiles into the sea off its east coast on Saturday, the South Korean military said, the latest in a series of launches in recent weeks.
A US official said the two missiles North Korea had fired appeared to be similar to launches in recent weeks.
Saturday's launch, the seventh by North Korea since US President Donald Trump and North Korean leader Kim Jong-un met at the inter-Korean border in June, have complicated attempts to restart talks between US and North Korean negotiators over the future of Pyongyang's nuclear weapons and ballistic missile programmes.
The two leaders agreed to restart working-level negotiations in June, but since then the United States has so far been unsuccessful in attempts to get talks going.
US envoy on North Korea Stephen Biegun was in Seoul this week to discuss ways to get negotiations back on track.
"We are prepared to engage as soon as we hear from our counterparts in North Korea," Mr Biegun said on Wednesday.
But in recent weeks, North Korea has repeatedly criticised US and South Korean largely computer-simulated joint military drills, South Korea's import of high-tech weapons such as F-35 stealth jets, and US testing of its intermediate-range cruise missile as threatening and hindrances to dialogue.
On Friday, North Korea's top diplomat called US Secretary of State Mike Pompeo a "diehard toxin," saying: "We are ready for both dialogue and standoff."
South Korea's National Security Council (NSC) expressed "strong concern" over North Korea's continued launches despite the fact that the South Korea-US joint military exercises denounced by North Korea had ended. It called for North Korea to stop escalating military tensions on the Korean Peninsula.
The NSC agreed to make diplomatic efforts to bring North Korea to the negotiating table with the United States as soon as possible for the complete denuclearisation of the Korean Peninsula, South Korea's presidential office said in a statement.
A senior US administration official said: "We are aware of reports of a missile launch from North Korea, and continue to monitor the situation. We are consulting closely with our Japanese and South Korean allies."
Japanese Defence Minister Takeshi Iwaya said that North Korea's missile launches were a clear violation of UN resolutions and cannot be ignored. He confirmed that missiles fell outside Japan's Exclusive Economic Zone, and posed no immediate threat to Japan's security.
South Korea's Joint Chiefs of Staff (JSC) said North Korea fired what appeared to be short-range ballistic missiles on Saturday at around 6:45 a.m. and 7:02 a.m. KST respectively from around Sondok, South Hamgyong Province. Sondok is the site of a North Korean military airfield.
They flew about 236 miles and reached a height of 60 miles, JSC said.
Japan's Coast Guard warned shipping not to approach any fallen debris.
South Korea officially informed Japan on Friday of its decision to scrap an intelligence-sharing agreement, which Japanese Minister of Defence Takeshi Iwaya said was regrettable and showed that Seoul failed to appreciate the growing security threat posed by North Korea.