Terrified Malaysians fled a town where dead gunmen lay in the streets on Monday as authorities ramped up security to combat a bizarre invasion by Philippine followers of a self-styled sultan.
A total of 27 people have been reported killed after two deadly shootouts in the state of Sabah on Borneo island where militants landed on February 12, claiming the state for the heir to a former Philippine sultanate.
Prime Minister Najib Razak, whose government was scrambling to contain Malaysia's worst security crisis in years, authorised a "doubling" of police and armed forces deployed in the tense state.
"An additional two army battalions have been dispatched to Sabah," Najib, who has vowed to root out the intruders, was quoted as saying by state news agency Bernama.
Malaysians have been shocked by the incursion, which began three weeks ago when an estimated 100-300 intruders were cornered by police and the military in the remote farming village of Tanduo.
A Friday shootout there killed 12 intruders and two police.
But fears of a wider guerrilla infiltration have escalated after another weekend gun battle in Semporna, a town that is hours away by road, in which six people and six gunmen died, according to authorities.
An AFP reporter in Semporna saw the corpses of three suspected gunmen with gunshots wounds, covered in flies and a foul stench as dozens of people were packing up their belongings and fleeing the town.
Residents said the bodies were gunmen killed by police.
"Our peaceful town has become a nightmare to live in," Julasri Yaakob, 38, told AFP as he heaved a bag full of clothes onto a lorry, his young daughter next to him.
"We are moving out because these are uncertain times. We heard the gunshots. My children are afraid," he said.
The armed intrusion has deeply embarrassed Najib -- who must call elections by June -- by exposing lax border security and fuelling perceptions of lawlessness and huge illegal immigration in Sabah.
At least 18 suspected militants and eight police officers have been killed in the gunfights, while authorities say another gunman was beaten to death Saturday by villagers in Semporna.
Followers of the 74-year-old Manila-based Islamic leader, Jamalul Kiram III, say the gunmen are ready to die to defend his claim to Sabah, which was once controlled by the now-defunct sultanate.
Supporters of the Filipino intruders took their campaign to cyberspace on Monday, manipulating Google listings to post a message backing the incursion.
A Google search for "Sabah" came back with a results page that displayed a "Wikipedia" entry preview calling Malaysian control of the state "illegitimate."
Philippine news portals have said a number of sites in the country also were defaced by pro-Malaysia hackers.
The exact identities of the gunmen remains a mystery, but Malaysian armed forces chief Zulkifeli Zin told a news conference in Sabah on Sunday that they appeared to have guerrilla combat experience.
The adjacent southern Philippines has been wracked for decades by Muslim insurgencies.
Authorities in Muslim-majority Malaysia have called for calm, saying the situation was under control, but have come under fire from the political opposition over the police deaths.
In Semporna, schools, stores and government offices were closed, but there was little sign of a heavy security presence in the town despite the recent clashes and fleeing population.
Sabah has seen previous smaller-scale cross-border raids from Islamic militants and other bandits from the Philippines.
The Sulu sultanate's power faded about a century ago but it has continued to receive nominal Malaysian payments for Sabah under a lease deal inherited from European colonial powers.