KUALA LUMPUR, Malaysia (AP) — Malaysia rejected a Philippine Muslim clan’s call for a ceasefire between security forces and Filipino gunmen in Borneo on Thursday, saying only an unconditional surrender would resolve clashes that have killed at least 28 people.

Malaysia mounted airstrikes and mortar attacks Tuesday against nearly 200 members of a Philippine Muslim clan who took over an entire Malaysian village to lay claim to a sprawling Borneo state they insist is theirs by royal birthright. The conflict has wreaked political havoc for both Malaysia and the neighboring Philippines.

Malaysian soldiers join an assault near the area where a stand-off with Filipino gunmen took place, at Tanduo village in Lahad Datu. Pic: AP.

Most of the clansmen eluded capture in a coastal district brimming with palm oil plantations and forested hills in Sabah state. On Thursday, government and police officials said they were tightening naval patrols off Sabah, evacuating thousands of villagers away from possible danger and detaining people suspected of being informants or food suppliers for the Filipinos.

The clansmen are led by a brother of Jamalul Kiram III, who claims to be the sultan, or hereditary ruler, of the southern, predominantly Muslim province of Sulu in the Philippines.

After the U.N.’s chief urged a peaceful resolution, the Filipino group said Kiram ordered the group to observe a unilateral ceasefire starting Thursday afternoon by holding their current position and taking a defensive posture.

“We hope Malaysia will reciprocate,” said Abraham Idjirani, a Philippine-based representative for the clansmen. “We are showing to the whole world that first the sultan wants to resolve this peacefully.”

Prime Minister Najib Razak said Malaysia would accept only unconditional surrender.

“They have to surrender their arms. They have to do it as soon as possible,” Najib said at a nationally televised news conference.

“Don’t believe this offer of a ceasefire by Jamalul Kiram,” Malaysian Defense Minister Ahmad Zahid Hamidi wrote on Twitter. “For the sake of the people of Sabah and Malaysia, eliminate all militants first.”

At least 28 people, including eight Malaysian policemen, have died mainly in shootouts between security forces and the Filipino group and their suspected allies. The clansmen sneaked into Sabah by sea from the nearby southern Philippines around Feb. 9.

Idjirani said a ceasefire would be in line with a statement of concern by U.N. Secretary General Ban Ki-moon late Wednesday.

Ban “urges an end to the violence and encourages dialogue among all the parties for a peaceful resolution of the situation,” according to the statement issued by Ban’s representative.

Ban voiced concerns about how the crisis might affect civilians, including Filipino migrants in Sabah, and urged “all parties to facilitate delivery of humanitarian assistance and act in full respect of international human rights norms and standards,” according to the statement.

Malaysia’s government has insisted it made every effort to coax the Filipinos to leave and had to use force after the group fatally shot two policemen last week. Six other police officers were ambushed and killed by other Filipinos believed to be linked to the clansmen in another Sabah district. The Malaysians have killed at least 20 clansmen and their suspected allies.

The Filipinos say Sabah once belonged to their royal sultanate for more than a century and should be handed back. Malaysia has dismissed their long-dormant territorial claim to the oil-and-timber-rich state, which has been part of Malaysia for five decades.

An estimated 800,000 Filipinos, mostly Muslims from insurgency-plagued southern provinces, have settled in Sabah over the years to seek work and stability.