SEOUL, South Korea >> North Korea fired four suspected short-range missiles into its eastern waters Thursday, South Korean defense officials said, in an apparent effort to protest ongoing U.S.-South Korean military exercises that Pyongyang calls a rehearsal for invasion.

The launches, however, weren’t expected to raise tension as North Korean routinely tests short-range missiles and it has recently sought better ties with South Korea in what outside analysts say is an attempt to win badly-needed foreign investment and aid. The rival Koreas this month held their first reunions of Korean War-divided families in more than three years.

The projectiles that landed off the North’s eastern coast were believed to be short-range missiles with a range of more than 200 kilometers (about 125 miles). The South Korean Defense Ministry officials who discussed the launches spoke anonymously, citing ministry rules.

The officials said they were trying to learn exactly what North Korea launched and that South Korea has bolstered its monitoring on North Korea.

Yonhap news agency, citing an unidentified military official, reported the North Korean projectiles were suspected to be ballistic Scud missiles or an upgraded version of its newly developed surface-to-ship KN-02 missiles.

Kim Yong-hyun, a professor of North Korea studies at Seoul’s Dongguk University, said the launches won’t be a prelude to provocation. He said the North appears to have intended to protest the South Korean-U.S. military drills that began Monday or to grab international attention as there has been little progress over a push to resume disarmament-for-aid negotiations.

Yang Moo-jin, a professor at the University of North Korean Studies in Seoul, said the North also carried out such launches to examine its weapons.

Last year, North Korea furiously reacted to the same South Korean-U.S. military drills by issuing a torrent of fiery rhetoric and threats to launch nuclear missiles against Seoul and Washington. Last year’s drills came after North Korea conducted its third nuclear test. The U.S. took the unusual step of sending nuclear-capable bombers in a show of its resolve to protect its ally.

North Korea hasn’t issued any harsh rhetoric against the current drills after their start. Seoul and Washington have said the annual drills are defensive in nature.

Pyongyang earlier threatened to scrap the arrangement for the family reunions in anger over the drills but later allowed them to proceed after high-level talks with Seoul. South Korea on Monday offered sending vaccines and disinfectants to North Korea after the country recently reported its first outbreak of foot-and-mouth disease since January 2012.

Earlier Thursday, North Korea presented to the media a South Korean missionary who it says was arrested last year for allegedly trying to establish underground Christian churches in the country. South Korea urged North Korea to quickly release him.

The Korean Peninsula officially remains at war because the 1950-53 Korean War ended with an armistice, not a peace treaty. About 28,500 American troops are stationed in South Korea to deter potential aggression from North Korea.

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Associated Press writers Youkyung Lee and Jung-yoon Choi contributed to this report.