He said that with the congressional debate settled, the authorities could now focus on restoring “public safety and law and order in the whole of Mindanao.”
But critics say Mr. Duterte does not need the additional powers of martial law to defeat the militants. And analysts say he appears to be using the Marawi crisis as an excuse to impose authoritarian rule in the Philippines, one of Asia’s most freewheeling democracies.
“Extending martial law can unmask the Duterte government’s real political intentions to apply authoritarian rule in the country, like the way he ruled Davao City for 20 years as a city mayor,” said Rommel Banlaoi, the chairman of the Philippine Institute for Peace, Violence and Terrorism Research.
He added, “Extending martial law can undermine civilian authorities and the existing democratic process in the country.”
Mr. Banlaoi argued that the use of martial law was justified only as a temporary measure, when the government was dealing with an emergency situation. “But the aftermath of the Marawi siege has not yet created a similar situation in other cities,” he said, “and extending martial law is an exaggeration of the use of coercive power of the state.”
Senator Risa Hontiveros, who voted against the extension, said that while she believed the threat of terrorism was real in Marawi, Mr. Duterte’s military officials had failed to present a compelling argument.
“Absent any plausible explanation, I can only reach one conclusion: Martial law has no strategic contribution to the military’s antiterrorism operations in Marawi,” she said.
But the House speaker, Pantaleon Alvarez, said the vote reflected what a majority of the public believed was necessary to prevent the violence from spreading. Mr. Alvarez pointed out that even if the Marawi crisis ended, there was still the lingering threat of retaliatory violence from the Abu Sayyaf and Maute groups, which laid siege to Marawi while backed by fighters from Southeast Asia and the Middle East.
In his letter requesting an extension, Mr. Duterte said it appeared that the militants’ leaders had survived military assaults on Marawi, including near-daily bombing runs that turned parts of the once-vibrant city of 200,000 into a virtual ghost town.
He also said that of the 600 militants known to be fighting in Marawi, about 220 were still entrenched in four neighborhoods in the city’s central business district. His statement contradicted the military’s estimate that 60 fighters remained holed up in the area.
The fighting has left 99 soldiers, 421 militants and 45 civilians dead, and Mr. Duterte said on Friday that the gunmen appeared to be holding about 300 people hostage.
“I told the military, we’ll just have to wait it out,” he said. “I told them, ‘Do not attack.’ Three hundred people — that’s 300 lives. If we have to wait there for one year, let us wait for one year.”
Abu Sayyaf’s commander, Isnilon Hapilon, who is the declared leader of the Islamic State group in the Philippines, and the brothers Omarkhayam and Abdullah Maute also remained at large despite earlier reports from the army that Omarkhayan Maute had been killed.
A Malaysian militant, Mahmud Ahmad, who is believed to be the groups’ go-between for Islamic State funds from the Middle East, was also believed to still be in Marawi.
The gunmen are armed with high-powered and military-grade weapons, and the local fighters are backed by foreign militants, including 20 Indonesians, the president said.