North Korea has fired two KN-06 surface-to-air missiles into the Yellow Sea, the South Korean defense ministry said on Thursday.
On April 3, Pyongyang fired four short-range missiles (with a range of 100 km) into the sea.
North Korea also fired seven surface-to-air missiles with a range of 300 km in March.
Earlier Japanese and South Korean media reports said that North Korea could be preparing for the launches of Nodong ballistic missiles with an estimated range of 1,300 km.
A report published by the US-Korea Institute at the Johns Hopkins School of Advanced International Studies on Tuesday said Pyongyang has around 1,000 ballistic missiles.
They include Nodong medium-range ballistic missiles (MRBM) with a range of 1,200-1,500 km and Scud ballistic missiles that could carry a nuclear payload 300-600 km.