Duterte, who was on a trip to Russian Federation to meet with Vladimir Putin, will cut his trip short and return home.
Gunfights ensued, killing at least two soldiers and one police officer and injuring 12 other members of the security forces. Secretary of Foreign Affairs Alan Peter Cayetano will stay behind to meet with Medvedev.
Philippine President Rodrigo Duterte declared the country's south under martial rule for 60 days and cut short a visit to Moscow on Tuesday after Muslim extremists allied with the Islamic State group laid siege to a southern city.
The Maute Group "burned several facilities, including a Roman Catholic church, the city jail, and a school", he said, adding that "the Maute fighters still occupy the main street of Malawi City and two bridges leading to the city". The United States lists it as a terrorist organisation.
After more than 20 years as mayor of Davao, Duterte won the presidential election last May with promises to rid the country of drugs and crime, to kill every drug dealer and user, and to feed their corpses to the fish in Manila Bay...
The US State Department offers a $5-million bounty for Hapilon's capture.
Brigadier General Rolando Bautista, commander of the Philippines' First Infantry Division, said security forces were trying to locate the militants.
The President, however, has appealed to the public to remain calm yet vigilant following reports troops clashed with members of the Maute group in Marawi.
These include the Maute group, which is based near Marawi. "The government is in full control of the situation and is fully aware that the Maute/Isis and similar groups have the capability, though limited, to disturb the peace; these have shown no hesitation in causing havoc, taking innocent lives and destroying property".
Mindanao is home to a number of Muslim rebel groups seeking more autonomy.
Fighting in Marawi comes weeks after the USA government issued a travel advisory to tourists about "kidnapping operations targeting foreign nationals" in the Palawan Province in western Philippines.
Meanwhile, the top priority of Mr. Duterte's landmark visit to Moscow this week is to acquire precision-guided bombs to use on Islamic militants in Mindanao and to seal a Memorandum of Understanding (MoU) to beef up Philippine defense.
The US and other Western governments also warned this month that terrorists plan to kidnap foreigners in tourist hotspots in Mindanao and the central Philippines.
Given that track record, there is concern Duterte will not tread lightly given the additional powers of martial law.