Jane Onyanga-Omara

USA TODAY

North Korea fired two mid-range ballistic missiles on Wednesday, South Korea’s military and U.S. authorities said.

U.S. Strategic Command said it detected what it thought was the simultaneous launch of the missiles, CNN reported.

One of the Rodong missiles is thought to have landed in Japanese waters after flying about 620 miles while the other exploded shortly after launch, South Korea's Yonhap news agency reported.

South Korea's Joint Chiefs of Staff said the missiles were launched toward waters off North Korea's east coast at 7.50 a.m. local time.

Seoul said it was the first time that a North Korean missile fell in Japan's exclusive economic zone (EEZ), about 155 miles west of northeastern Japan's Akita Prefecture, indicating the secretive state is testing the range of its Rodong missiles, Yonhap reported.

Japanese Prime Minister Shinzo Abe said the missile "posed a grave threat to our country's security. It is an unforgivable, reckless act," he said, the Kyodo news agency reported.

Wednesday’s launch came after the North fired three missiles on July 19 after Seoul and the United States agreed to deploy an advanced U.S. missile defense system in South Korea by the end of 2017.

The office of South Korean President Park Geun-hye said Wednesday that she will attend an economic forum in Vladivostok in Russia next month and discuss the North’s nuclear program with President Vladimir Putin.