North Korea has fired two more short-range rockets into the sea, the latest in a series of recent missile tests.
The rockets were fired off the east coast and flew about 180km (110 miles), South Korean military officials said.
The move comes as the Chinese president prepares to visit South Korea, with whom the North is technically at war.
It also comes a day after Japan urged Pyongyang to stop such launches and after Seoul rejected a North Korean offer to end hostilities as insincere.
The two rockets were fired from a site near the eastern city of Wonsan at 06:50 (21:50 GMT Tuesday) and 08:00, South Korea's Joint Chiefs of Staff said in a statement.
North Korea appeared to be testing the range of the projectiles, Yonhap news agency reported, citing military officials. It also carried out similar tests on 26 and 29 June.
To date North Korea has carried out three nuclear tests and is believed to be working on long-range missile development. In recent months it has also carried out a steady stream of short-range missile tests.
Talks between its leaders and other nations on ending its nuclear ambitions have been stalled for years.
China, which is North Korea's biggest trading ally, is the nation believed to wield the most influence over Pyongyang.
But Beijing appears increasingly frustrated with its unreliable neighbour.
The issue of North Korea - including possible plans for a fourth nuclear test - is expected to top the agenda during President Xi Jinping's visit to Seoul, which begins on Thursday.
North Korea has also in recent weeks alternated between threatening the South and offering apparent concessions.
The two nations remain technically at war because the 1950-53 Korean War ended in an armistice, not a peace deal.
On Monday Pyongyang offered to suspend hostile military activities and slander, a move Seoul described as "nonsensical".
North Korea has made similar offers in the past but these have invariably broken down.
North Korea is also currently engaged in talks with Japan on the issue of Japanese nationals it abducted in the 1970s and 1980s to teach language and culture to its spies.
Japan criticised Sunday's rocket launch at the start of one-day talks in Beijing on Tuesday, at which no breakthroughs were reported.