The Filipino government placed Mindanao, an island of 22 million people, under martial law on May 23 "to crush" militant groups linked to Daesh.
Philippine President Rodrigo Duterte has asked Congress to extend martial law in the southern island of Mindanao until the end of the year, his spokesperson said on Tuesday.
The government applied martial law to Mindanao, an island of 22 million people, on May 23 "to crush" militants from the Maute and Abu Sayyaf groups, which took over parts of Marawi City.
The militants have put up fierce resistance, with scores still holed up in Marawi's commercial heart.
The crisis has killed more than 500 people and displaced at least 260,000.
Mindanao-based journalist Noel Tarrazona discusses the extension.
"The primary objective of the possible extension is to allow our forces to continue with their operations unhampered by deadlines and to focus more on the liberation of Marawi and its rehabilitation and rebuilding," said presidential spokesman Ernesto Abella, reading a letter to Congress signed by Duterte.
The brazen takeover of Marawi by organised, heavily armed militants who have pledged allegiance to Daesh has been the biggest crisis of Duterte's one-year presidency.
While few dispute that Duterte has a serious problem on his hands, critics have derided his declaration of martial law across all of Mindanao, parts of which are at peace and are home to numerous foreign companies.
Martial law is a sensitive issue in the Philippines, bringing back memories of the 1970s rule of late dictator Ferdinand Marcos, who was accused of exaggerating security threats to justify measures that allowed his regime to suppress dissent brutally.
Duterte has praised Marcos on numerous occasions and critics say he relishes being likened to a dictator, which plays into his tough image.