South Korea's presidential office plans to penalize Japan's Kyodo News agency for carrying a report on President Lee Myung-bak's visit to the eastern islets of Dokdo earlier than allowed last week, the presidential spokesman said Thursday.

News media accredited to the presidential office are banned from publishing specific reports on the president's schedule outside of the presidential compound in advance under "comprehensive embargo" regulations designed for security reasons.

Kyodo, however, reported Lee's plan to visit Dokdo a night earlier on Thursday.

"What we have figured out so far is that Kyodo sent the story while aware of the comprehensive embargo rule," presidential spokesman Park Jeong-ha told reporters. "This is a violation of regulations."

The presidential office plans to issue a "heavy" penalty after giving Kyodo a chance to make its case, Park said without elaborating.

Possible penalties include accreditation cancellation or suspension. (Yonhap News)