Japan PM

He said he did not want his illness to get in the way of decision making, and apologised to the Japanese people for failing to complete his term in office.

The 65-year-old has suffered for many years from ulcerative colitis, an inflammatory bowel disease, but he said his condition had worsened recently.

Last year, he became Japan's longest serving prime minister. His current period in office began in 2012.

He will remain in his post until a successor is chosen.

Mr Abe had said he called the election a year early in order to increase his mandate amid a number of "crises" facing the country.

Among them was the increasing threat from Pyongyang.

The initial exit polls suggested Mr Abe had done just that, retaining his two-thirds "super-majority".

This is vital to his ambition to revise Japan's post-war pacifist constitution - enacted by the country's American occupiers in 1947 - Article 9 of which calls for the complete renunciation of war.