BREAKING NEWS — South Korean media are reporting that North Korea may have conducted a nuclear test.

YTN television is citing an unnamed government official and the Yonhap news agency cites a ruling party member as saying the nuclear test may have occured Monday morning.

South Korean President Lee Myung-bak has convened an emergency meeting.

North Korea had recently said it would again test a nuclear device — its first was in October 2006 — in reaction to tightened international sanctions after it fired a long-range rocket in April.

News of the test hit South Korean financial markets, sending the main KOSPI share index down four percent in late morning trade, while the won dropped more than 1 percent against the dollar.

The Associated Press and Reuters contributed to this report.