After declaring sixty days of martial law on the island province of Mindanao, President Rodrigo Duterte cut short his Russia visit and hinted he could extend the state of emergency to other parts of the country. Mindanao is the second largest and southernmost major island in the Philippines and home to 22 million people.

"I may decide to expand the area to include the Visayas because it is just walking distance (from Mindanao) and they can always escape there to begin another terrorist activity," Duterte said, referring to militants linked with self-proclaimed "Islamic State" (IS) terrorist group.

Army tanks moved into the southern Philippines on Thursday after gunmen set fire to buildings, seized hostages and raised a black IS flag in Marawi, the capital city of the province of Lanao del Sur on the island of Mindanao. Much of Marawi, with a population of 200,000, was still a no-go zone Thursday as air force helicopters flew overhead.

Duterte also said he might put all of the Philippines under martial law and impose curfew in several conflict-ridden areas.

"We have reached dangerous levels. With martial law, I will solve all Mindanao problems," said the president, who is often in news for his aggressive political style and a violent anti-drug campaign .

The Philippine constitution limits the martial law period up to 60 days but Duterte said it could last up to a year.

On Tuesday, violent clashes broke out between security forces and militants linked with IS, leaving at least one police officer dead.

The bloodshed began when police and soldiers raided an apartment in the southern city of Marawi where Isnilon Hapilon, an alleged leader of the notorious Abu Sayyaf gang and the Philippine head of IS, was suspected of hiding.

Abuse of power

"The imposition of martial law will send a strong signal to militants that the government is in control of the situation. But the authorities have to rely on the security forces that are overstretched, and if you remove constitutional protections, there is a danger of power abuse," Jose Antonio, a Manila-based security analyst and military historian, told DW.

"Duterte didn't need to declare martial law to address the situation. But this is typical of his character. His style of governance is authoritarian and he does not tolerate dissent. He is moving the country toward a complete martial law," Antonio added.

Opposition parties have warned Duterte against expanding military powers.

"The reported declaration of martial law in Mindanao is subject to revocation by the members of the House of Representatives and Senate. This cannot be set aside by the president," Congressman Edcel Lagman said in a statement.

Chaos in Marawi

Meanwhile, thousands of Marawi residents are fleeing to safer areas. The markets are closed and there is no electricity in the city. People are worried about running low on food and other life-saving supplies.

"Everyone is trying to get out of the city. People are using trucks and cars to leave the city but many roads have been closed off by the military," Halil Amerol, regional director of the Bangsamoro Development Agency, told DW.

Nadia, an English teacher in the city, was one of those who tried to get out of the city after hearing about the military's possible air strikes.

"We couldn't leave because we didn't have a vehicle. We couldn't walk because I have five small cousins with me. I'm trapped here. We have to stay here for at least another night," Nadia told DW, adding that Marawi was a small and densely-populated city and the airstrikes would be devastating.

The Philippine National Police confirmed Wednesday that four public buildings, including a prison in Marawi, were set on fire by militants. Six police officers have reportedly been killed.

Four civilians have been taken hostage. Among them is Father Chito Suganob, who was taken hostage in the Cathedral of Our Lady Help of Christians by the members of the Maute group.

"At the time of his capture, Father Chito was performing his religious duties. His capture violates the norms of a conflict," said Father Soc Villegas, president of the Catholic Bishops Conference.