North Korea fired a missile into the sea off its east coast on Friday, the South's military said, hours after the leaders of South Korea, Japan and the United States warned Pyongyang to end provocations or face more pressure.
The projectile was fired from a region near the North's east coast, a South Korean military official said by telephone.
It was a short-range surface to air missile, another official at the office of the Joint Chiefs of Staff said, adding the military was trying to determine the range.
The launch at around 12:45 pm local time (0345 GMT) comes hours after US President Barack Obama joined South Korean President Park Geun-hye and Japanese Prime Minister Shinzo Abe in vowing to add pressure on the North for its recent activities.
Meeting on the sidelines of a global nuclear security summit in Washington, the three leaders recommitted their countries to each others' defence and warned they could take further steps to counter threats from Pyongyang.
Obama held separate talks with President Xi Jinping of China, the closest North Korea has to an ally, and said they both wanted to see "full implementation" of the latest UN sanctions against Pyongyang. But Xi offered no sign that Beijing was prepared to go beyond its consent to the Security Council measures imposed in early March.
The North has fired a string of rockets in recent weeks including a long-range rocket in February that launched an object into space. Leader Kim Jong Un has supervised some of the launches in defiance of UN sanctions.
North Korea conducted its fourth nuclear test on Jan. 6, leading to new Security Council sanctions in early March. South Korea and the United States have imposed separate sanctions.
Earlier on Friday, South Korea said North Korea has been sending signals to disrupt GPS reception in the South, leading some shipping vessels to return to port.