Malaysia has launched air strikes and mortar attacks against nearly 200 Filipinos occupying a Borneo seaside village in a dramatic escalation of a bizarre three-week siege that has turned into a security nightmare for both Malaysia and the Philippines.

The assault follows firefights in Malaysia's eastern Sabah state that killed eight police officers and 19 Filipino gunmen who in February snuck in by boat and claimed the land as part of a sultanate under a Filipino clan leader.

The Malaysian national police chief, Ismail Omar, said Malaysian security forces suffered no casualties in Tuesday's offensive but he did not give details about the Filipinos. Air strikes "achieved their objectives in accordance to the targets" while ground forces who encountered resistance from gunmen firing at them were carrying out "mopping up" operations by searching houses in the village, Ismail said, without elaborating on how many had been detained.

The clansmen, armed with rifles and grenade launchers, had refused to leave, staking a long-dormant claim to the entire state of Sabah, which they insisted was their ancestral birthright.

"The government has to take the appropriate action to protect national pride and sovereignty as our people have demanded," the Malaysian prime minister, Najib Razak, said after the raid began in a statement issued through the national news agency, Bernama.

Authorities had been trying to resolve the siege peacefully since the presence of the group in Lahad Datu district became known on 12 February. Talks were held to encourage the intruders to leave without facing any serious legal repercussions, Najib said.

"The longer this intrusion persisted it became clear to the authorities that the intruders had no intention to leave Sabah," Najib said. "As a peace-loving Islamic country that upholds efforts to settle conflicts through negotiations, our struggle to avoid bloodshed in Lahad Datu did not work."

Najib later said in a public speech that the offensive began with air strikes followed by mortar attacks conducted by both the police and military.

The Filipinos who landed in Lahad Datu, a short boat ride from the southern Philippines, insisted Sabah had belonged to their royal sultanate for more than a century. The group is led by a brother of Jamalul Kiram III of the southern Philippine province of Sulu.

Abraham Idjirani, a spokesman for the Filipinos, told reporters in Manila that the group would not surrender and that their leader was safe. Idjirani said he spoke by phone with Kiram's brother, who saw fighter jets dropping two bombs on a nearby village that he said the group had already abandoned.

"They can hear the sounds of bombs and the exchange of fire," Idjirani said. "The truth is they are nervous. Who will not be nervous when you are against all odds?"

He said they will "find a way to sneak to safety". "If this is the last stand that we could take to let the world know about our cause, then let it be," Idjirani said, describing the Malaysian assault as "overkill".

The Philippines had asked Malaysia to try to avoid further bloodshed.

In Manila, a presidential spokesman, Ricky Carandang, said the foreign secretary, Albert del Rosario, was in Kuala Lumpur meeting with his Malaysian counterpart. "We've done everything we could to prevent this but in the end Kiram's people chose this path," Carandang said.

An undetermined number of other armed Filipinos are suspected to have encroached on other districts within 200 miles (300km) of Lahad Datu.

Groups of Filipino militants have occasionally crossed into Sabah to stage kidnappings, including one that involved island resort vacationers in 2000. Malaysia has repeatedly intensified its patrols but the long and porous sea border with the Philippines remains difficult to guard.

The crisis could have wide-ranging political ramifications in both countries. Some fear it might undermine peace talks brokered by Malaysia between Manila and the Moro Islamic Liberation Front, the main Muslim rebel group in the southern Philippines.

It also could affect public confidence in Malaysia's long-ruling National Front coalition, which is gearing up for general elections that must be held by the end of June. The coalition requires strong support from voters in Sabah to fend off an opposition alliance that hopes to end more than five decades of federal rule by the National Front.