Philippines President Benigno Aquino is visiting a southern city where Muslim rebels, apparently opposed to peace talks, have seized several neighborhoods and taken civilian hostages.
A presidential spokesman said on Twitter that Aquino arrived early Friday to "personally assess the situation on the ground" in Zamboanga City, a key port town of almost 1 million people.
Philippine troops there are battling about 200 rebels linked to the Moro National Liberation Front who stormed the city Monday, taking in scores of hostages who officials say are being used as human shields.
At least nine people have been killed in the fighting, which has forced around 13,000 residents to flee.
Clashes have also broken out on nearby Basilan island, where rebels have carried out two days of attacks on military targets. The Philippine military said troops deterred a rebel attack during a 2-hour gun battle early Friday in the city of Lamitan. It said six soldiers were wounded.
The MNLF has long pushed for greater autonomy in the mainly Muslim south, where more than 150,000 people have died during a four decade-long insurgency.
The group signed a peace agreement with the government in 1996 that led to the creation of the Autonomous Region in Muslim Mindanao. But some of its members continued to fight, claiming Manila did not hold up its end of the deal to develop the impoverished, rural region.
MNLF founder Nur Misuari has also criticized the government's peace talks with a breakaway faction, the Moro Islamic Liberation Front. Fearing the negotiations may marginalize his own group's power, Misuari last month declared parts of the region to be independent of Manila.
But it is not clear to what extent Misuari is involved in the current standoff, as he has not appeared in public or issued any official statement. In a Facebook statement, Mayor Beng Climaco says she spoke with Misuari, and that he has "disowned" the actions of the hostage takers.
Some government officials have denied that charge, claiming Misuari did order the attacks.
Under Misuari's leadership, the MNLF in 2001 carried out a similar attack in Zamboanga. The fighters were later allowed to leave after releasing their hostages.