Philippine President Rodrigo Duterte yesterday made light of his penchant for daytime dozes after his office said "power naps" had caused the gruff leader to miss a number of key meetings at a Singapore summit.

Duterte is attending the annual Association of Southeast Asian Nations (Asean) meeting alongside a string of world leaders including Russia's Vladimir Putin, Japan's Shinzo Abe, Chinese Premier Li Keqiang and US Vice-President Mike Pence.

But on Wednesday, the mercurial leader missed four of the eleven meetings he was slated to attend, as well as a gala dinner hosted by Singaporean Prime Minister Lee Hsien Loong.

"What's wrong with my nap?" the 73-year-old told reporters as he arrived at the summit venue yesterday morning for another long day of meetings.

Asked if he felt fully rested he replied: "Still not good enough, but enough to sustain the endurance for the last days."

Duterte's no-shows on Wednesday prompted a statement from his office explaining he had only had three hours of sleep the night before.

"He took power naps to catch (up) on sleep," presidential spokesman Salvador S. Panelo said, adding that "some quarters are making a big fuss of the president skipping a few meetings".