A member of Philippine President Rodrigo Duterte's guard unit was shot dead, but the president was far away at the time of the incident and the head of his security team ruled out a political motive.

Tuesday morning's shooting in Malacanang Park, the Manila base of the Presidential Security Group (PSG), is being treated as an isolated incident, PSG commander Lope Dagoy said.

The body of the 37-year-old PSG guard was discovered by his wife in his quarters at 8:50am (00:50 GMT). He died from a single gunshot wound to the chest.

"We are ruling out foul play," Dagoy told reporters.

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Duterte's whereabouts had not been known for several hours prior to Dagoy's remarks. The mercurial president was not seen in public on Monday and prior to that had been in his southern home city of Davao, for several days.

Asked during a regular briefing about Duterte's whereabouts at the time of the shooting, his spokesman Ernesto Abella said: "We don't have any information regarding that".

Duterte is notoriously unpredictable and often causes confusion with sudden changes to his crowded public schedules, which typically start in the afternoon and can run as much as four hours late, often because of his long, unscripted speeches.

He usually spends his weekends in Davao City, sometimes starting as early as Thursday and not returning to Manila until Monday or later.

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He was due to attend several public events in Manila on Tuesday evening.

Malacanang Park is close to Duterte's Bahay ng Pagbabago residence, separated from his Malacanang palace by the Pasig river.

Dagoy said police were now investigating the shooting and the PSG did not want to speculate about the circumstances.

He condoled with the guard's family on behalf of the unit.