Prime Minister Shinzo Abe, Japan’s longest-serving Premier, announced his resignation because of poor health on Friday, ending a stint at the helm of the world’s third-biggest economy in which he sought to revive growth and bolster its defences.

Abe has battled the disease ulcerative colitis for years and two recent hospital visits within a week had fanned questions on whether he could stay in the job until the end of his term as ruling party leader, and hence, premier, in September, 2021.

“I cannot continue being Prime Minister if I do not have the confidence that I can carry out the job entrusted to me by the people,” Abe, 65, told a news conference as he announced his decision to step down.

He said he wanted to avoid a political vacuum as the country copes with the novel coronavirus.

“I apologise from the bottom of my heart that despite all of the support from the Japanese people, I am leaving the post with one full year left in my term,” Abe said, at times blinking back tears and his voice choking up.

It was the second time Abe has resigned as Prime Minister because of poor health.

As news of the resignation spread, Japan's benchmark Nikkei average fell 2.12 per cent to 22,717.02, while the broader Topix shed 1.00 per cent to 1,599.70. The selling wiped $47 billion off Tokyo’s $5.7 trillion stock market value.

The resignation will trigger a leadership race in the ruling Liberal Democratic Party — most likely in two or three weeks — and the winner must be formally elected in parliament.