President Rodrigo Duterte has extended by four months the term of service of Armed Forces of the Philippines Chief of Staff General Rey Leonardo Guerrero.

Guerrero will remain in the military sevice until April 24 next year, Presidential Spokesperson Harry Roque said on Thursday.

"AFP Chief of Staff General Guerrero will reach his age of compulsory retirement on December 17, 2017, and the President has extended his service to April 24, 2018, as per Republic Act No. 8186, or six months since he assumed office as AFP Chief of Staff," he said in a statement.

Guerrero's appointment as chief of staff was approved by the Commission on Appointments on Wednesday.

Roque said the executive secretary, by authority of the president, has signed on December 6, Guerrero's extension of the service.

Guerrero replaced General Eduardo Ano in October when he reached the mandatory retirement age of 56.

Under Section 5, paragraph 5, Article XVI of the 1987 Constitution, "laws on retirement of military officers shall not allow extension of their service."

Paragraph 7 of the same provision also states, "the tour of duty of the Chief of Staff of the armed forces shall not exceed three years. However, in times of war or other national emergency declared by the Congress, the President may extend such tour of duty."

The Philippines has been under the state of national emergency on account of lawless violence in Mindanao since September 2016.

Mindanao has also been under martial law since Duterte declared it on May 23 this year following the attack of Islamic State-inspired terrorists in Marawi City.

War-torn Marawi, which was only freed from terrorists in October, is undergoing rehabilitation.

Duterte has yet to decide if he would extend martial law in Mindanao after its imposition expires on December 31. Celerina Monte/DMS