The Chinese government, the major partner of the Pyongyang regime, was now "concerned" about the escalation of tension on the Korean peninsula and urged both sides to "remain calm"
North Korea launched missiles that landed in court Sea of South Korea, which responded by sending F-15s and exchanging fire on their disputed western sea border.
Seoul sent planes to the area and residents of a South Korean island fled to bomb shelters in the most dramatic escalation of tensions since 2010.
A North Korean shell landed in South Korean waters, but none made landfall in South Korea, unlike 2010 when a bombing killed two soldiers and two civilians.
A North Korean bombardment mock led Marines in South Korea on a nearby island to return fire, a South Korean official said. Seoul sent F-15 fighter jets to patrol its side of the border, media said.
It was unclear how many shots were fired by either side.
The exchange occurs amid increased tensions over North Korea after the Security Council United Nations condemned Pyongyang for its missile launches midrange last week, and at a time when South Korea leaders, Japan and the United States meet to discuss the weapons program of North Korea.
The area where the gunfire occurred near the Northern Limit Line call, made at the end of the Korean War from 1950 to 1953, North Korea has refused to recognize.
Previous meetings between the two navies in the area have killed dozens of sailors from both sides.
traslation: Belén Zapata