Islamic State terrorists stormed a cathedral in the Filipino city of Marawi Tuesday, attempting to seize control of the city as well as taking a Catholic priest and more than a dozen churchgoers hostage. At least 21 have been reported killed in the fighting.

The ISIS terrorists seized Rev. Chito Suganob and members of his congregation amid a raging battle with government troops. Archbishop Socrates Villegas, president of the Catholic Bishops Conference of the Philippines, said the terrorists threatened to murder the hostages if the government did not recall the “forces unleashed against them,” reported the Associated Press. Suganob urged Filipinos to pray for the hostages’ safe return.

Filipino government officials said the situation was under control, but residents of Marawi—who fled the area—gave conflicting accounts, insisting the terrorists had the upper hand. Filipino President Rodrigo Duterte instituted martial law in the south of the country due to the terrorists’ siege of Marawi, and cut short a trip to Russia in order to deal with the crisis.

“To my countrymen who have experienced martial law, it would not be any different from what President Marcos did. I’d be harsh,” Duterte said in a video message recorded on his return flight to the Philippines, referring to the rule of 1970s Filipino dictator Ferdinand Marcos.