Japanese Prime Minister Shinzo Abe returned to work on Wednesday after a three-day summer break that included a hospital visit, leading to speculation he is suffering ill health.

"I underwent a checkup the day before yesterday to take full care of my health. I am returning to work now and I hope to work hard," Abe said as he entered the prime minister's office in the afternoon.

Japanese Prime Minister Shinzo Abe speaks to reporters at his office in Tokyo on Aug. 19, 2020. (Kyodo)

Speculation about the 65-year-old's health has been swirling after he spent more than seven hours at Keio University Hospital in Tokyo on Monday. The visit followed a recent magazine report that said he vomited blood in July.

A hospital source said Abe underwent tests on Monday as a follow-up to a checkup he underwent in June.

Some members of Cabinet and others close to Abe have expressed concern that the prime minister has been showing signs of exhaustion after months leading Japan's response to the coronavirus pandemic.

Abe worked for nearly 150 days straight from late January through late June and took three days off last month.

He remained in Tokyo for all six days spent away from his duties in July and August as the Tokyo metropolitan government has requested residents refrain from traveling outside the capital on summer vacations to prevent a further spread of the virus.

Almost a third of the total infections in Japan have been reported in Tokyo.

In his previous stint as prime minister, Abe abruptly resigned his post in 2007 due to an intestinal disease called ulcerative colitis but said later he had overcome the illness with the help of a new drug. He was returned as leader in 2012.

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