ZAMBOANGA, Philippines » Philippine officials negotiated Friday (Thursday in Hawaii) with Muslim rebels who were holding more than 100 people hostage, as President Benigno Aquino III warned that his government won’t hesitate to use force to end the five-day standoff.

Aquino visited troops and some of the 24,000 people displaced by the violence in southern Zamboanga city, where about 200 fighters from a Muslim rebel faction stormed into several coastal communities earlier this week and took residents hostage. Twenty-two people, including 15 rebels, have been killed so far in repeated clashes between the guerrillas and the troops who have surrounded them.

Fighting broke out again in Santa Catalina village on Friday, and ABS-CBN TV reported that voices presumably of hostages were heard shouting "cease fire, cease fire!" One government soldier was reportedly wounded.

A mortar fired by the rebels landed on a street in front of the government hospital in Santa Catalina. An AP photographer near the scene saw at least six people wounded, including four Red Cross personnel and two soldiers. The wounded were rushed away on stretchers and an ambulance.

Four fires raged in different parts of Zamboanga, a major southern port city. Officials said the rebels could be setting them as diversions.

Military spokesman Lt. Col. Ramon Zagala said that lines of communication with the rebels remain open but they’re still refusing to surrender.

"We’re negotiating," Zagala said, refusing to elaborate.

The crisis began Monday when Moro National Liberation Front rebels, who have been overshadowed by a rival group in talks with the government for a new minority Muslim autonomy deal, clashed with troops who had foiled their plan to march through Zamboanga city and hoist their flag at city hall.

The rebel leader, Nur Misuari, signed a peace deal in 1996, but the guerrillas did not lay down their arms and later accused the government of reneging on a promise to develop long-neglected Muslim regions in the predominantly Roman Catholic nation. The government says Misuari kept on stalling and making new demands.

"We will investigate all the actuations of Misuari," Aquino told reporters, adding that his justice secretary was evaluating evidence against Misuari.

Misuari has not been seen in public since the standoff began.

"There are lines they should not cross," Aquino said of the rebels. If those lines are crossed, the government will be obligated to use "the force of the state," he said.

Associated Press writers Teresa Cerojano, Jim Gomez and Hrvoje Hranjski in Manila contributed to this report.