MANILA — Malaysian security forces killed 31 Filipino gunmen on the island of Borneo, officials said Thursday, and the government rejected calls by the United Nations for an end to the fighting.

At least 60 people, including eight Malaysian police officers, have been killed in the nearly monthlong conflict over an effort by followers of a Philippine-based sultan to assert a historical claim over parts of Borneo Island.

“The secretary general is closely following the situation in Sabah, Malaysia,” said a statement from the United Nations released on Wednesday. “He urges an end to the violence and encourages dialogue among all the parties for a peaceful resolution of the situation.”

A spokesman for Jamalul Kiram III, the leader of the group fighting in the Malaysian state of Sabah, said the sultanate was declaring a unilateral cease-fire in reaction to the call by the United Nations.