Three soldiers were killed on Thursday as fighting with Muslim rebels who laid siege to a bustling port city in the southern Philippines spread to a nearby province, the military said.
Nine soldiers were also wounded in clashes with members of the Moro National Liberation Front (MNLF) in Lamitan town in Basilan province, 900 km south of Manila, said Lieutenant Colonel Ramon Zagala, a military spokesman.
“This is possible spillover to ease the tension and divert attention from Zambaonga City,” Mr Zagala added.
The MNLF fighters were holed up in six of the 98 neighbourhoods in Zamboanga City, having taken an estimated 100 hostages.
More than 13,000 residents have been displaced by the violence in Zamboanga City since Monday. Schools, offices and banks were shut, while flights and ferry services have been suspended.
The violence erupted when about 200 MNLF rebels clashed with troops as they gathered for a protest march against the failure of the government to implement a 1996 peace agreement.