Five Malaysian policemen and two gunmen have died in a fresh clash on Borneo island, police said Sunday, as fears mounted that violence linked to a deadly standoff with Filipino intruders was spreading.

The shootout late Saturday in the town of Semporna followed a firefight a day earlier between Filipino followers of a self-proclaimed sultan and Malaysian security forces that left 12 intruders dead along with two police officers. The latest clash in Malaysia's biggest security crisis of recent years occurred when police were "ambushed" by gunmen, national police chief Ismail Omar told reporters.

Semporna is 300 kilometres (190 miles) from Tanduo village, where an estimated 100-300 people have been encircled by Malaysian police and soldiers since landing by boat from the Philippines on February 12 to claim the area for their leader.The 74-year-old Manila-based leader, Jamalul Kiram III, claims to be heir to the Islamic sultanate of Sulu, which once controlled parts of the southern Philippines and the modern-day Malaysian state of Sabah on Borneo island.

Malaysian officials called for calm but various reports painted a picture of chaos in the area.It was not immediately made clear whether the Semporna attackers were still at large. Meanwhile Malaysian media quoted Ismail as saying police were pursuing yet another group of armed men in Kunak, another town in the region.

The new incidents sparked Malaysian fears of a wider campaign by other intruders or their supporters in Sabah, which has large numbers of Filipino immigrants - both legal and illegal.The Philippine embassy in Kuala Lumpur issued a statement urging calm among Filipinos. "We feel and understand the anxieties felt by many of you at these difficult times," it said."This is not the time to undertake any action that might be misunderstood by some parties."

The situation is delicate for the Southeast Asian neighbours.The Philippine government is looking to consolidate recent progress in mending fences with Islamic separatists in its partly Muslim south.The government of Muslim-majority Malaysia, meanwhile, could face pressure at home if harsh action is taken against the Islamic Filipino intruders, which also could inflame Sabah's many Filipinos.

Following Friday's firefight Malaysian police threatened "drastic action" if they did not surrender.Philippine President Benigno Aquino, who has sharply criticised the intruders, has also urged them to give up.But Kiram's spokesman Abraham Idjirani repeated Sunday his followers would not budge. He said the sultan would seek the intervention of the United States, which colonised the Philippines in the early 1900s."(Malaysians) want to hide the truth - that they do not own Sabah. It is owned by us," he said in an interview on Philippine radio.

Sabah state police chief Hamza Taib said several villagers in Semporna beat to death a man armed with a grenade launcher who had gathered several people at a mosque on Sunday, Malaysia's The Star newspaper reported.The sensational events have embarrassed Malaysian Prime Minister Najib Razak - who must call elections by June - by exposing lax border security and fuelling perceptions of lawlessness and massive illegal immigration into Sabah.

Lim Kit Siang, a top opposition leader, said the government was not being forthcoming enough with information from Sabah and the police fatalities "could have been avoided if the whole situation had been properly handled".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.Kiram's people are demanding Malaysia recognise that the sultanate owns Sabah and share profits from economic development in the state.