Witnesses reported Saturday that Philippine military jets fired rockets on suspected militant positions in the besieged city of Marawi, as the government vowed to continue driving out militants linked to the so-called "Islamic State" (IS) jihadist group.

The latest siege on the Muslim-majority city comes at the start of the Muslim holy month of Ramadan.

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 "We will try our best to clear the area at the soonest possible time," regional military commander Lieutenant General Carlito Galvez said. "We apologize to our Muslim brothers for interfering with the first day of Ramadan."

Philippine President Rodrigo Duterte imposed 60 days of martial law on Tuesday across Mindanao, the country's second-largest island and home to an impoverished Muslim minority, after Islamist insurgents laid siege to Marawi on Tuesday and even hoisted the IS flag in parts of the city.

At least 48 people have died and an estimated 80-90 percent of Marawi's 200,000 residents have already fled the city since hostilities started this week, according to Mamintal Alonto Adiong Jr., vice governor of the Lanao Del Sur province.

"This is really very painful for us Muslims," he told the Deutsche Presse-Agentur news agency. "Ramadan is supposed to be a celebration for us, but we can't feel its spirit now."

Military spokesman Colonel Jo-ar Herrera said: "It is painful for the Maranao [the name for local Muslims] that it is Ramadan, but our action now is to protect Marawi. These are the impacts of the local terrorist group's actions."

Duterte vows to wipe out Islamist extremists

The Philippine president on Friday ordered his troops to crush the militant IS fighters, adding that he had long feared the country could be at risk from "contamination by IS."

Nevertheless, Duterte also indicated he would be willing open a dialogue with the Islamist militants. "My message mainly to the terrorists on the other side is we can still solve this through dialogue," Duterte said on Friday. "And if you cannot be convinced to stop fighting, so be it. Let's just fight."

Presidential spokesman Ernesto Abella said Duterte's offer was made in the spirit of Ramadan. "Together we pray for an end to terrorism that falsely claims to advance Islam and seeks to subjugate our land to the brutal IS," Abella said in a statement. "In this spirit of Muslim peace, the president has offered the hand of peaceful dialogue to terrorist groups, to avoid bloodshed in this time of prayer, fasting and mercy."

However, officials admitted that the chances of such are very slim.

President decried for rape joke

Duterte also came under fire for reportedly joking that he would take responsibility for the crimes and abuses committed by troops under martial law, including the raping of women.

"If you go down, I go down. But for this martial law and the consequences of martial law and the ramifications of martial law, I and I alone would be responsible, just do your job, I will take care of the rest," Duterte said in a speech to troops in Iligan, a city near Marawi.

Referring to any soldiers who commit violations, he then joked: "I'll imprison you myself. If you had raped three, I will admit it, that's on me."

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Duterte is known for often making deeply offensive remarks and loading his speeches with profanity, threats and jokes about taboo subjects.

Friday's remarks were not the first instance Duterte had joked about rape. In the lead-up to last year's presidential election, he recalled the rape and murder of an Australian missionary in 1989 in the city Davao, where he was mayor at the time. Duterte reportedly called the victim beautiful and said that, as mayor, he should have been first in line.

dm/jlw (AP, AFP, dpa)