"I'm apologizing to the Japanese people for this political uneasiness," Maehara said at the news conference where he made the announcement.

The foreign minister had been under scrutiny for a political contribution he received from a South Korean living in Japan. Under Japanese law, politicians cannot accept any money from foreigners. The money given to Maehara, 50,000 yen ($600), came from a lifelong friend.

Maehara had met with Japan's prime minister to alert him of his decision and had the leader's consent to do so, a foreign ministry spokesman said.

He had been in office for six months. He was appointed in September, when Prime Minister Naoto Kan reshuffled his Cabinet to consolidate his power base after a landslide win to lead his party.

Maehara formerly served as the minister for land, infrastructure, transport and tourism.

CNN