Mr. Duterte declared martial law on May 23 following a bloody siege of the southern city of Marawi by Islamic State group-aligned militants.

Philippine President Rodrigo Duterte asked Congress on Tuesday to extend martial law in the southern third of the country until the end of the year, saying the rebellion there will not be quelled by July 22, the end of his 60-day martial law proclamation.

Mr. Duterte declared martial law on May 23 following a bloody siege of the southern city of Marawi by Islamic State group-aligned militants, the most serious security crisis he has faced since assuming power in June last year.

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In a letter to the Senate and the House of Representatives read by his spokesman Ernesto Abella on Tuesday, Mr. Duterte said that after consulting security officials, he has concluded that the rebellion in the south will not be quelled completely by July 22.

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Under the constitution, in case of invasion or rebellion, when public safety requires it, the President can declare martial law for no more than 60 days. He can ask Congress to extend such a proclamation to a period of time to be determined by the lawmakers.

More than 550 people, including 413 militants, have been killed in nearly two months of fighting in Marawi, a bastion of Islamic faith in the south.