( CNN ) -- A day after launching airstrikes and mortar shells in a remote part of the island of Borneo , Malaysian security forces searched house-to-house Wednesday for gunmen from the Philippines who infiltrated the area last month and clashed with police . The group of Filipino men is believed to number between 100 and 300 . It arrived three weeks ago on the east coast of the Malaysian state of Sabah , on Borneo , demanding recognition as representatives of an old sultanate that ruled the area . Efforts by Malaysian and Philippine authorities to persuade the men to return peacefully to their homes in the nearby southern Philippines failed , and the standoff descended into clashes last week that reportedly left 28 people dead , including nine police officers . Malaysian security forces said their offensive Tuesday , which involved fighter jets , mortars and ground troops , achieved its objectives . However , they did not disclose the number of Filipino fighters captured or killed in the operation , and the Filipino group said the Malaysian attack failed to inflict any casualties . On Wednesday , Malaysian police and armed forces combed the area around Kampung Tanduo , the village where the Filipinos had originally been holed up , in an attempt to flush out the gunmen , according to Bernama , Malaysia 's national news agency . Alarm in Malaysia . The crisis in Sabah alarmed Malaysians over the ease with which the intruders entered the country from the nearby southern Philippines , where a number of Muslim rebel groups are based . It has also revived an unresolved territorial issue between the Philippines and Malaysia . The Malaysian forces ' task of tracking down the gunmen has been complicated by the Filipinos ' efforts to blend in with the local population , Ismail Omar , the head of Malaysian Police , said at a news conference Wednesday , according to Bernama . Ismail said one gunman was believed fatally shot early Wednesday after ambushing Malaysian security forces , but that the other attackers had retrieved his body . There are strong ethnic ties between many inhabitants of Sabah and the southern Philippines . People and goods regularly go back and forth across the porous sea border between the two . The Filipino men have called themselves the Royal Army of the Sultanate of Sulu , a former Islamic power in the region that once controlled parts of the Philippines and Borneo . Its influence has since faded , and it is now a clan in the restive southern Philippines . The sultanate 's leadership has been driven by internal power struggles in recent decades , but the squabbling family members appear to have united in the recent decision to send their followers to Sabah and stake a claim to their former territory . 'No casualties ' Abraham Idjirani , a spokesman for one of the sultanate 's leaders in Manila , said he had spoken twice Wednesday with the leader of the armed group in Sabah , who reported that the men were in `` good condition '' and prepared for another possible attack . He claimed the group had suffered no casualties from the assault Tuesday because the Malaysian planes had bombed an area vacated by Filipinos . The sultanate is still open to talks , but the group in Sabah will not return to the Philippines , Idjirani said . The situation on the ground appears to be getting more complex with reports that other Filipino fighters , sympathetic to the sultanate 's cause , are joining the group in Sabah , despite efforts by Malaysia and the Philippines to tighten sea patrols in the area . Idjirani said Tuesday that other people from the region were joining the sultanate 's followers , although he did n't know who they were . And Nur Misuari , a founding leader of the Moro National Liberation Front ( MNLF ) , a Muslim rebel group that signed a peace deal with the Philippine government in 1996 after decades of armed rebellion , said he believed former fighters from the organization were with the sultanate 's followers in Sabah . He said if any current MNLF members had gone there , they had done so without authorization . A faded power . Established in the 15th century , the Sultanate of Sulu became an Islamic power center in Southeast Asia that at one point ruled Sabah . But the encroachment of Western colonial powers , followed by the emergence of the Philippines and Malaysia as independent nation states , steadily eroded the sultanate 's influence . Sulu is now a province within the Republic of the Philippines . But the historical connection still fuels tensions between Malaysia and the Philippines , with Manila retaining a `` dormant claim '' to Sabah through the Sultanate of Sulu , according to the CIA World Factbook . The Philippines claims much of the eastern part of Sabah , which was leased to the British North Borneo Company in 1878 by the Sultanate of Sulu . In 1963 , Britain transferred Sabah to Malaysia , a move that the sultanate claimed was a breach of the 1878 deal . Malaysia still pays a token rent to the sultanate for the lease of Sabah .
Malaysian forces try to flush out Filipino fighters on Borneo . The Philippine group says it suffered no casualties from an attack Tuesday . - Malaysia Airlines Flight 17 was shot down over eastern Ukraine by a Russian-made missile fired from rebel-held territory in the area of Luhansk. Between 100 and 300 Filipinos arrived by boat on the Malaysian coast in February .