North Korea has fired two unidentified missiles, its fourth such launch in less than two weeks, South Korea's military has said. They were fired from South Hwanghae province across the peninsula into the sea to the east, a statement said, the BBC reported on Tuesday.
The US said it was monitoring the situation and consulting with South Korea and Japan.
North Korea has expressed anger at US-South Korean military exercises that got under way on Monday.
The annual drills have been kept low key but North Korea says they violate agreements reached with President Donald Trump and South Korea's President Moon Jae-in.
In a statement, the North's Foreign Ministry accused the two allies of "playing all sorts of tricks" to justify the military exercises and said their "aggressive nature" could not be covered up.
North Korea has been the subject of a series of US and international sanctions over Pyongyang's development of nuclear weapons and a series of missile tests.
Last Friday the North test-fired what South Korean officials said appeared to have been a new type of short-range missile.
Those two missiles landed in the Sea of Japan, also known as the East Sea, according to South Korea's Joint Chiefs of Staff (JCS).
The JCS said the missiles flew very low and travelled about 220 km. Analysts said they appeared to have been unusually fast.
On Wednesday, the North launched two missiles that flew 250 km and reached a height of 30 km before landing in the Sea of Japan, according to South Korea.
On July 25, North Korea had fired two other missiles, one of which travelled about 690 km.
That was the first launch since President Trump and North Korean leader Kim Jong-un held an impromptu meeting in June at the demilitarised zone (DMZ), an area that divides the two Koreas, where they agreed to restart denuclearisation talks.
(With inputs from IANS)