SEOUL (Reuters) -North Korea fired one short-range ballistic missile and another ballistic missile on Monday, South Korean military said.

The first short-range ballistic missile was fired to the northeast around 5:05 a.m. Seoul time (2005 GMT) from near Changyon, South Hwanghae Province in North Korea. Another unknown ballistic missile was detected around 5:15 a.m., South Korea's Joint Chiefs of Staff said.

The South Korean military is fully prepared and closely sharing information with the U.S. and Japanese authorities while strengthening surveillance and vigilance in preparation for any further launches, the top military officials said in a statement.

On Sunday, North Korea criticised a joint military exercise by South Korea, Japan and the United States held last month and warned of "overwhelming response" against such drills.

North Korea said last week it had successfully conducted an important test aimed at developing missiles carrying multiple warheads, a claim rejected by South Korea as "deception" to mask a failed launch.

(Reporting by Ju-min Park and Joyce Lee; Editing by Leslie Adler and Lisa Shumaker)

By Ju-min Park and Joyce Lee