Philippines President Rodrigo Duterte on Tuesday declared martial law in the country’s southern province of Mindanao after clashes broke out between Islamic State group militants and armed forces in Marawi city. Duterte’s spokesperson, Ernesto Abella, made the announcement in front of media persons in Moscow, where the president is currently on a visit.

Philippines Foreign Minister Alan Peter Cayetano said that while the president’s meeting with his Russian counterpart Dimitry Medvedev stood cancelled, Duterte will remain in Russia, Reuters reported.

Reports surfaced that the radical group’s black flag was hoisted atop two vehicles patrolling the southern city’s streets surfaced, according to Huffington Post. The militants have reportedly seized control over Amai Pakpak Medical Center, and replaced the Philippine flag with the black flag, the CNN quoted local reports.

Residents have been advised to stay indoors. Officials, however, have asked citizens to avoid spreading rumours about the alleged seizure, Reuters reported.