North Korea fired two ballistic missiles in a northeastern direction on Monday, South Korea's military said, with one of the launches possibly failing and the missile falling inland within the country.

The Joint Chiefs of Staff (JCS) said one short-range ballistic missile was launched from the Jangyon area in South Hwanghae Province around 5:05 a.m. and flew about 600 kilometers, landing in waters off the North's northeastern city of Chongjin, reported Yonhap news agency.

Another ballistic missile was launched from the same area at around 5:15 a.m. and flew only about 120 kilometers before its trail disappeared from radar. news agencyCol. Lee Sung-jun, spokesperson of the JCS, told a briefing the second missile may have flown abnormally during the early stage of its flight and that if it exploded in midair, its debris could have fallen inland.

"We are conducting a comprehensive analysis on various possibilities," Lee said when asked if the missile had exploded or fallen inland. He declined to comment on where it may have come down.

The launch came a day after the North's foreign ministry denounced a joint exercise between South Korea, the United States, and Japan, saying the country would take "offensive and overwhelming" countermeasures against what it called an attempt to strengthen a military bloc.

The three-day multidomain Freedom Shield exercise, which ended Saturday, involved fighter jets and warships, including a U.S. aircraft carrier, in international waters south of South Korea's southern resort island of Jeju.

The latest launch also took place five days after the North fired a ballistic missile toward the East Sea on Wednesday.

The North claimed the next day to have successfully conducted a multiple warhead missile test, but the South has dismissed the claim as "deception," saying the launch failed as the missile exploded in midair.

The latest launch also took place amid growing concerns over deepening military cooperation between Pyongyang and Moscow after North Korean leader Kim Jong-un and Russian President Vladimir Putin signed a "comprehensive strategic partnership" treaty during a summit last month in Pyongyang.

The pact includes a pledge for the two countries to come to each other's aid if attacked.

The launch raised speculation it could be a test for missiles intended to be sent to Russia, considering the KN-23 is suspected to have been used by Moscow. Lee declined to comment when asked about the possibility.

Seoul and Washington have accused Pyongyang of delivering arms to Moscow to fuel its war against Ukraine. Defense Minister Shin Won-sik has said the arms trade between North Korea and Russia is expected to expand after their leaders sign the treaty.

North Korea has ratcheted up cross-border tensions in recent weeks, launching trash-carrying balloons to South Korea in a tit-for-tat move against anti-Pyongyang leaflets sent by North Korean defectors and activists in the South.

--IANS