The trip by Leni Robredo to an evacuation centre in Balo-i for residents who escaped a month-long conflict in nearby Marawi City adds to speculation about the health of 72-year-old President Rodrigo Duterte, whose absence this month from the public eye is the longest since he took office a year ago.
Known for a packed public schedule and marathon speeches several times a day, Duterte's disappearances during what has been the biggest crisis of his presidency will add to frequent rumours he is in poor health, which his office denies.
Robredo made no mention of Duterte during her visit, when she said she hoped life for the nearly 250,000 people displaced by fighting between troops and rebels allied with the ISIS group could soon return to normal.
"All of us are hoping that the fighting will soon end so the people can go back to their respective homes," she told reporters. "The government has been doing everything that we can. We can only hope that this will end soon."
Duterte's spokesman did not respond to a request for comment on his lengthy absence.
Salvador Panelo, a longtime friend of Duterte's and his top legal advisor, said the president was as "strong as a bull" and would attend a public event and meet cabinet members on Tuesday.
Duterte was last seen on June 20 in two cities close to Marawi, when he met soldiers and evacuees. That followed a three-day absence after a speech in which he said his health was "immaterial", amid raised eyebrows about his failure to show in public for Independence Day on June 12.
His office has said he has been experiencing fatigue, and his aide Christopher "Bong" Go on June 15 posted images on social media of Duterte signing documents, and standing in front of a television showing a news bulletin.
Fighting resumed in Marawi today, a day after a unilateral truce was declared by the military for eight hours to mark the Eid al-Fitr Islamic holiday and try to rescue civilians trapped in the conflict zone.
The resilience and the level of organisation of the Maute group and its affiliates has caused consternation in the region about the extent to which ISIS's extremist agenda may have gained traction in the southern Philippines, a region more familiar with banditry and separatism than radical ideology.
Duterte had long warned that it was only a matter of time before there would be an ISIS contamination.
The battle for Marawi has claimed the lives of 70 servicemen, 27 civilians and 290 militants, according to official figures.
Fleeing residents and some local disaster officials believe many more civilians may have been killed while trapped in areas battered by artillery and air strikes, and infested with Maute snipers. Witnesses have reported seeing bodies in the streets for days, some decomposing.
The military said it was concerned about reports of the possible beheading of hostages, or captives being forced to take up arms against government troops.
Spokesman Jo-Ar Herrera said soldiers were committed to finishing the job and saving residents, 13 of which were rescued on Sunday.
"Our offensive operations have resumed and will continue so we can liberate Marawi in the soonest time possible," he told reporters.
"We are focused and committed and will accomplish our mission."
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