The missile tests, reported by the Yonhap news agency quoting sources, comes a day after North Korea, apparently responding to the polices of South Korean President Lee Myung-bak's conservative government, expelled South Korean officials from the joint Kaesong industrial park located north of the two countries' heavily guarded border.

The South Korean government appeared unconcerned by the missile tests.

"The government regards North Korea's missile firing as merely a part of its ordinary military training," a presidential spokesman told Yonhap.

Recent report have said Lee plans to take a tougher stand than his predecessors on inter-Korean cooperation. That would include the North making progress in the stalled six-party denuclearization talks.