North Korea has recently carried out a series of missile tests
North Korea has fired two suspected short-range missiles into the sea, South Korea says, in the fourth such test in two weeks.
The projectiles were launched from a western province into waters east of the Korean peninsula in the early hours of Wednesday, officials said.
The move follows a recent visit by the Chinese president to South Korea.
Chinese leaders traditionally go to Pyongyang before Seoul, and the visit has been seen as a snub to North Korea.
"North Korea fired two short-range missiles presumed to be Scud-type ones... from a site in Hwanghae province in a north-easterly direction," South Korean spokesman Um Hyo-sik was quoted as saying by Yonhap news agency.
"They flew some 500km (310 miles) and landed in international waters," he added, without giving further details.
North Korea has carried out several such launches in recent months, including four within the last two weeks.
It has interspersed these launches with apparently conciliatory moves towards the South, including a recent offer to suspend provocative military activities and cross-border slander.
Previous similar offers have come to nothing and South Korea has dismissed this latest offer.
NUCLEAR ARCHITECT DEAD
The latest launch also comes days after Chinese President Xi Jinping and his South Korean counterpart Park Geun-hye reaffirmed their opposition to North Korean nuclear tests during talks in Seoul.
China - North Korea's biggest trading ally - is the nation believed to wield the most influence over the government in Pyongyang. Xi's decision to visit Seoul first is being seen as a message to North Korea.
To date North Korea has carried out three nuclear tests and is believed to be working on long-range missile development.
Talks between its leaders and other nations on ending its nuclear ambitions have been stalled for years.
North and South Korea, meanwhile, remain technically at war because the 1950-53 Korean War ended in an armistice, not a peace deal.
The latest missile tests came on the same day North Korea announced the death of a key nuclear architect.
General Jon Pyong-ho, who was included in the United Nations' sanctions list last year, helped lead Pyongyang's ballistic missile and nuclear weapons programmes.
Gen Jon, 88, died of a heart attack on Tuesday, the official Korean Central News Agency said. He will be given a state funeral led by North Korean leader Kim Jong-un.
He was credited with making a special contribution to converting North Korea "into a satellite producer and launcher and a nuclear weapons state", an official obituary said.