(The New York Times) - Seven people were reported killed, and four hostages taken, as fighting continued Sunday in the Malaysian state of Sabah over a historic claim to the area by a religious group from the southern Philippines.

The Malaysian government said the police and military presence in the area was being doubled, while the religious group said an undetermined number of supporters from the southern Philippines had entered the area to reinforce those supporting the claim.

The Malaysian and Philippine navies have stepped up patrols in the waters between Sabah and the southern Philippines, which can be traversed in a speedboat in a little more than an hour.

Five Malaysian police officers and two of their attackers were killed in an ambush Saturday, officials said Sunday. The Malaysian state news agency Bernama reported Sunday that villagers near the ambush had beaten to death a man suspected of being one of the attackers. That brought the death toll from fighting in the area to at least 21.

On Friday, 12 members of the Filipino religious group and 2 Malaysian commandos were killed during a failed attempt to capture the group that had been holding a small village on the eastern coast of Borneo island since Feb. 12.

A spokesman for the group, whose members claim to be heirs to the sultanate of Sulu, which ruled parts of northern Borneo for centuries, said Sunday that its forces on Sabah had taken hostage a Malaysian police officer, two soldiers and a government official.

"We advised the people on the ground to take care of them, to feed them, so that in case there shall be international agencies to investigate the matter we can present those four captured government officials of Malaysia as witnesses to the atrocities committed by the government of Malaysia," the group's spokesman, Abraham Idjirani, said Sunday.

Bernama quoted Prime Minister Najib Razak on Sunday as saying the violence had been limited to three areas of Sabah: Lahad Datu, where the group originally arrived, and the nearby areas of Semporna and Kunak.

"The people of Sabah should not be fearful of their safety," the prime minister was quoted as saying.

He added that Malaysian forces were operating in the areas affected by the violence. "Let's give them the opportunity and time to carry out their operations and overpower the group and rescue those in need," he said.

On Sunday, Malaysian officials urged Sabah residents to remain calm and said resorts and other tourist facilities in the area remained open.

"More fatalities may be expected, and as a nation we must come together to rally behind our forces," said Liew Vui Keong, the deputy prime minister of Malaysia, according to Bernama.

Jacel Kiram, the daughter of Jamalul Kiram, who claims to be the sultan of Sulu, told a television station in Manila that the Malaysian authorities were rounding up Filipinos in the areas affected by the violence. Thousands of Filipinos live and work in Sabah.

"Yesterday, Malaysian police were indiscriminately capturing Filipinos," she said.

The Philippines has repeatedly asked the group to leave and has tried to calm tensions with its close ally. A Philippine diplomatic mission, headed by Jose Brillantes, a foreign affairs under secretary and former Philippine ambassador to Malaysia, has been sent to Kuala Lumpur to smooth relations.

Several descendants of the sultanate of Sulu claim to be the current sultan, and some disagree with the actions taken by the group fighting in Sabah.