TOKYO  — Japan’s defence minister on Friday said she had resigned over a long-brewing scandal involving the handling of military documents, in a political blow to Prime Minister Shinzo Abe.

Abe, who has seen his popularity plummet in recent weeks over a series of controversies, immediately apologised to the nation over the saga.

"I decided to resign as defence minister," Tomomi Inada told a press conference. "I submitted my resignation to the prime minister and it was accepted."

Inada, a close confidante of Abe who shares his staunchly nationalist views, was appointed defence minister in August 2016, a time when she was touted as a possible future leader.

But her nearly year-long stint has been characterised by repeated controversy, including increasing criticism of the ministry’s handling of log reports filed by Japanese peacekeepers in South Sudan showing worsening security.

Abe, who became prime minister for a second time in December 2012 with a vow to rejuvenate Japan’s economy, has been hit by scandals and gaffes involving members of his ruling Liberal Democratic Party (LDP).

"I apologise from the bottom of my heart to the people for this situation in which a minister resigns," Abe told reporters after the resignation.

"All responsibilities lie with me, the prime minister, in the appointment of cabinet ministers," Abe said, adding he "must seriously accept the people’s severe criticism".

The most recent setback to the prime minister has been claims he showed favouritism to a friend in a business deal, an accusation he has vigorously denied.  — AFP