SINGAPORE (Reuters) - Philippine President Rodrigo Duterte skipped several meetings at an Asia-Pacific summit in Singapore on Wednesday, prompting the 73-year-old’s office to issue a statement scotching speculation that it was due to ill health.

FILE PHOTO: President Rodrigo Duterte speaks after his arrival, from a visit in Israel and Jordan at Davao International airport in Davao City in southern Philippines, September 8, 2018. REUTERS/Lean Daval Jr./File Photo

“We assure the nation that his aforementioned absence has nothing to do with his physical health and wellbeing which have been the subject of speculation,” spokesman Salvador Panelo said in a statement.

“The president’s constantly punishing work schedule is proof that he is in top physical shape.”

Panelo named four scheduled events that Duterte had not attended on Wednesday, during which the president “took power naps” to catch up on sleep, and said he would also skip a gala dinner with the leaders of nine Southeast Asian nations, U.S. Vice President Mike Pence and several others.

Duterte’s health has been a constant source of speculation since he disappeared from public view for a week last year, and he has said openly that he is tired and would like to step down before the end of his term ends in 2022.

Last month Duterte’s office revealed that he had undergone a colonoscopy and he told reporters that a biopsy had shown he did not have cancer.

The constitution provides for the public to be told of the state of health of an incumbent president, if serious.

If a sitting president dies, is permanently disabled or removed through impeachment, the vice president succeeds to serve the remaining years in a six-year, single term.

Vice President Leni Robredo, a leader of the opposition, was elected separately in 2016. Speculation about Duterte’s health last month prompted concern that the Philippines could be headed for uncertainty given the highly polarized political climate.

Duterte has cited Robredo’s “incompetence” as a reason for his inability to quit as president.

Duterte has a record of skipping summit sessions, though he did not miss any as host when the Philippines held the chair of the Association of Southeast Asian Nations (ASEAN) last year.

Panelo said it was “amusing that some quarters are making a big fuss” of Duterte’s absences, noting that he had attended ASEAN meetings with leaders from China, Japan and Russia.

“Last night, the president worked late and had only less than three hours of sleep,” he said. “It is unfortunate that the first event scheduled today was at 8:30a.m.”

Duterte is known for having an unorthodox working schedule that typically starts mid-afternoon and includes cabinet meetings that can go on beyond midnight.