A group of heavily armed fighters from the terrorist group “Maute,” also known as the Islamic State of Lanao, attacked the city of Marawi in the southern Philippines on Tuesday. Two soldiers and a policeman were reportedly killed in the battle so far, along with an unknown number of militants.

Philippine President Rodrigo Duterte declared the region under martial law for 60 days and has cut short his visit to Russia to deal with the “rebellion,” as he called it. Marawi, which has a population of about 200,000, is located on the southern island of Mindanao.

The Associated Press quotes Defense Secretary Delfin Lorenzana warning that “the whole of Marawi City is blacked out, there is no light, and there are Maute snipers all around.” However, Lorenzana insisted the Philippine military has not lost control of the city.

According to military officials, the battle began when Philippine troops raided a hideout used by militant leader Isnilon Hapilon, who has been tapped by the Islamic State to run a branch of ISIS in Southeast Asia. The AP describes him as “an Arabic-speaking Islamic preacher known for his expertise in commando assaults.”

Hapilon is the leader of the Abu Sayyaf gang, which is notorious for its kidnapping operations. He is one of the U.S. Justice Department’s most wanted terrorists in the world, with a $5 million bounty on his head.

When Hapilon, who was wounded in an airstrike in January, realized his men were likely to be defeated by Philippine troops, he called in reinforcements from another ISIS affiliate called Maute, which sent an estimated 50 gunmen to help.

Other versions of the story, such as the one provided by the Philippine Star, say the battle began when troops were dispatched to check reports of “men brandishing assault rifles” and came under fire from militants.

Residents of Marawi took photos of Maute fighters marching through the streets and driving stolen police vehicles flying the black flag of ISIS. The militants occupied the city hall and hospital, freed a number of prisoners from the local jail, and set fire to schools and a Catholic church, among other outrages. The ISIS flag was seen hanging from the hospital during its occupation.

Some of these assaults were described by the Philippine military as diversionary tactics, intended to draw troops away from the effort to capture Hapilon.

Local officials told the people of Marawi to “stay home and drop to the ground if they hear gunshots.” The Sun-Star reports that thousands of people have nevertheless fled their homes, as the military moved in armored fighting vehicles and even appears to have conducted airstrikes against “selected areas of Marawi City, particularly in the border with Lanao del Sur beside Lake Lanao.”

“We are extremely concerned about the impact of the ongoing hostilities in Marawi City on the civilians,” said Pascal Porchet, head of the Red Cross delegation. “We urge all parties to the conflict to spare civilians and respect civilian property, such as hospitals and schools, in fulfillment of their obligations to respect international humanitarian law.”