President Duterte had requested the extension to combat remaining militants who want to establish an "Islamic State" base on the southern island of Mindanao. Ongoing fighting there has displaced half a million people.
Philippine lawmakers on Wednesday voted to extend martial law by one year on Mindanao island, a decision President Rodrigo Duterte had requested to fight Islamist extremism plaguing the region.
The Senate voted 14-4, while the House of Representatives voted 226-23 in favor of the extension.
Philippine President Rodrigo Duterte on Monday had asked the Philippine Congress to extend the martial law to ensure the "total eradication" of pro-"Islamic State" (IS) extremists.
Duterte said the remaining militants still hoped to establish a caliphate in the Philippines and Southeast Asia after government forces killed more than 900 fighters and quelled the five-month Marawi siege in October.
"I ask the Congress of the Philippines to further extend the proclamation of martial law and the suspension of the privilege of the writ of habeas corpus in the whole of Mindanao for a period of one year" from 1 January, the letter said.
The letter also said extending martial law in southern Mindanao would allow government forces to press offensives against other armed groups, including the Abu Sayyaf and communist guerrillas, who have intensified attacks.
A previous request to extend martial law in the southern area until the end of 2017 was approved in August.
The violence on Mindanao has displaced about half a million people and turned mosque-studded Marawi city into a war zone.
Duterte initially imposed military rule across the island, home to about 20 million people, in May to stop an uprising by IS militants in Marawi city.
Five months to defeat IS
It took a US-backed military campaign five months to defeat the militants, with the battle claiming more than 1,100 lives and leaving large parts of Marawi in ruins.
Some gunmen and commanders managed to escape during the fighting, the military said.
One of the militants who might replace Hapilon, Esmail Abdulmalik, who uses the nom de guerre Abu Turaife, is thought to be planning bombings in the south, Duterte said. An IS-linked faction in another militant band, the Bangsamoro Islamic Freedom Group, has intensified roadside bombings and attacks on troops.
Communist New People's Army guerrillas, meanwhile, have taken advantage of the military's preoccupation with Muslim extremists and increased their attacks on troops and businesses in the south, killing 41 government security personnel and destroying at least 2.2 billion pesos (€37 million, $43.6 million) in property, Duterte said.
Duterte last month called off peace talks with the communists, blaming continuing deadly attacks from the rebels.
amp/rg (AFP, AP, dpa)