FELDA SAHABAT, Malaysia (AFP) - Malaysia's prime minister on Thursday rejected a ceasefire call by the self-proclaimed Philippine sultan whose Islamic fighters launched a deadly incursion into Malaysia.
Malaysian forces are currently hunting for the Islamic militants in a remote region of Borneo island where they landed last month to assert a long-dormant territorial claim in what has become Malaysia's worst security crisis in years.
Their Manila-based leader called for ceasefire at midday but Prime Minister Najib Razak, who flew to the region Thursday to inspect security operations, said he told Philippine leader Benigno Aquino by phone the offer was rejected.
"I told President Aquino they must lay down their arms immediately," Najib told reporters in a village near the area where up to 300 militants were being searched for.
"They have to surrender their arms and they have to do it as soon as possible."
The "sultan", Jamalul Kiram III, declared a unilateral ceasefire for 12:30 pm (0430 GMT) and urged Malaysia to reciprocate.
But Najib said Malaysian forces would continue to press the offensive, adding that still more soldiers would be sent in to the hilly region of vast oil palm estates and pockets of jungle.
Anger has mounted in Malaysia over the incursion, which began February 12 when fighters arrived from the southern Philippines to press Kiram's claim to the area.
Kiram says he is heir to the Sultanate of Sulu, which once ruled islands that are now part of the southern Philippines, as well as Sabah.
An estimated 100-300 militants were holed up in the sleepy farming village of Tanduo for three weeks until a pair of deadly shootouts with security forces at the weekend triggered a military assault with jet fighters and ground forces Tuesday.
However, the attack appears to have merely scattered the fighters, and security forces were combing through huge palm groves for them. Sporadic exchanges of fire have been reported since the assault.
UN Secretary General Ban Ki-moon urged a peaceful resolution of the bizarre incursion, which has led to at least 28 reported deaths -- 20 militants and eight police officers.
"(Ban) urges an end to the violence and encourages dialogue among all the parties for a peaceful resolution of the situation," said a statement released by his office late Wednesday.
Kiram declared the "unilateral ceasefire... in order to reciprocate the call of the UN to preserve lives", said his spokesman.
Malaysia's military assault appears to have failed, with authorities confirming just one kill so far.
They have not explained how the militants -- said to be alive and well and in contact with their Manila comrades -- were able to escape a tight security cordon built up over three weeks.
Tension is running high in eastern Sabah due to the incursion, and residents of some towns have fled after police said gunmen were spotted in other areas down the coast, raising fears of a wider guerrilla infiltration.
Late Wednesday, police said the bodies of six police officers killed in a weekend ambush in the coastal town of Semporna were mutilated.
"The bodies of dead police personnel were found to have been brutally mutilated by the armed intruders," a statement said, giving no further details.
Police have said six militants responsible for the Semporna ambush were later killed by reinforcements.
The incursion has proven a delicate situation for the two neighbours, with Manila earlier calling for Malaysian restraint just before Tuesday's military assault was launched.Malaysian Foreign Minister Anifah Aman said late Wednesday that his government might seek Kiram's extradition if Manila failed to take action, but the Philippine government said that was unlikely, citing the lack of an extradition treaty.