"We have declared that the country is for Lebanon and sovereignty is for Lebanon, and whatever Lebanon decides or considers its higher interests, we support it."
Lebanon has vowed to wipe the Sunni group which has been battling government soldiers since Sunday. More than 80 people have been killed in the fighting, the country's worst internal violence since the 1975-1990 civil war.
Zeina Khodr, Al Jazeera's correspondent, said from Tripoli: "We are hearing reports that it is unlikely that the Lebanese army will go in and it will be the Palestinian factions who may be responsible for taking care of Fatah al-Islam and wiping them out in the words of the Lebanese government."
Fatah al-Islam has said it will abide by the ceasefire it declared on Tuesday but vowed its fighters will not turn themselves in.
"We respect the truce, but we will not surrender. If we are attacked, we will fight until the last drop of blood," Abu Salim, the group's spokesman, said.
A representative of the group told Al Jazeera that they could continue to fight for another nine months and could take the battle outside the camp.
Appeal for aid
Hajj Rifaat, an official from the mainstream Fatah faction, said residents of Nahr al-Bared would be offered refuge in the 16,000-resident Beddawi camp further south.
"But we will certainly be quickly overwhelmed if the flow of refugees continues at this rate," he said.
"The problem will quickly become one of being able to provide extra food."
In Tripoli, refugees were being taken into people's homes or being put up in schools, witnesses said.
Hoda Samra, spokeswoman for UN Palestinian refugee agency, said: "We are providing relief aid to the thousands of refugees who have sought refuge in our schools and centres in Beddawi and Tripoli."
"Our clinics are also working double shifts in order to cope with the number of refugees and provide them proper services."
John Holmes, the UN undersecretary-general for humanitarian affairs, appealed for humanitarian access and warned that no successful steps had been taken to ensure that civilians receive aid.
"From outside it's very easy to condemn the Lebanese army and government for what they are doing against Fatah-al-Islam"
Rabih, Mansourieh El Metn, Lebanon
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He also called Tuesday's attack on an a UN Relief and Works Agency convoy "outrageous and completely unacceptable". The convoy had come under fire as aid workers tried to deliver food and water to residents in Nahr al-Bared.
Residents of the camp have described a scene of devastation inside after three days of shelling by the Lebanese army.
"All the houses are destroyed. We left and we don't know what happened to ours. We walked most of the way here," Nizar Sharaf, who was carrying his four-year-old son, said.
Taleb al-Salhani, a security officer with the UNRWA, said the bodies of 20 civilians have been retrieved from the camp, but the total number of civilian casualties remained unknown.