Story highlights North Korea fired its fourth short-range missile in two days, South Korea tells news agency

Missiles were fired into the sea off the Korean Peninsula's east coast, Yonhap reports

Tensions in the region have eased since a peak last month

North Korea fired a short-range missile into the Sea of Japan on Sunday, according to South Korea's semiofficial news agency Yonhap, citing a South Korean military official.

On Saturday, North Korea launched three short-range guided missiles into the sea, also known as the East Sea, off the Korean Peninsula's east coast, Yonhap reported.

The missiles on Saturday were fired in a northeasterly direction, away from South Korean waters, the ministry said.

South Korea has beefed up monitoring on North Korea and is maintaining a high level of readiness to deal with any risky developments, the ministry added, according to Yonhap.

According to the Arms Control Association, a U.S.-based organization, short-range guided missiles are generally classified as those traveling less than 1,000 kilometers (about 620 miles).

Tensions in the region have eased since a period last month that included near daily North Korean threats of war.

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U.S. and South Korean officials feared at that time that Kim Jong Un's regime was planning to carry out a test launch of longer-range ballistic missiles, believed to be Musudans. The South Korean government says they have a maximum range of 3,500 kilometers (2,175 miles).

Andrew Salmon, a journalist and author based in the South Korean capital, Seoul, said North Korea's reported launch of short-range missiles Saturday should not cause the same degree of concern as the launch of a satellite or medium-range Musudan rocket.

"It's a short-range tactical weapon. If any other country launched this kind of weapon, it's a routine test, nobody would be too worried. It's really simply because it's North Korea doing this that it raises concerns," he said.

The situation is much less tense in the region than it was last month, Salmon said.

"The North Koreans have significantly de-escalated their bellicosity and their rhetoric since the end of April," he said. "The South Korean government, I suspect, will not be strongly condemnatory of this test because right now they are very, very keen to get the North Koreans to the negotiating table."

The recent tensions flared after the North's long-range rocket launch in December and underground nuclear test in February, both of which were widely condemned.

Pyongyang's fiery rhetoric intensified in March as the U.N. Security Council voted to tighten sanctions on the regime following the nuclear test.

Annual U.S.-South Korean military drills in South Korea also fueled the North's anger, especially when the United States carried out displays of strength that included nuclear-capable B2 stealth bombers.

North Korea is demanding recognition as a nuclear power, something the United States refuses to accept.

Last month's crisis resulted in the closure of the Kaesong Industrial Complex, the last major symbol of inter-Korean cooperation.