ZAMBOANGA, Philippines (AP) _ A letter purportedly from the kidnappers of an American linguist threatened to kill him unless the government meets eight demands, including the removal of foreign missionaries from Muslim areas.

Charles Walton, 60, of Philadelphia, was seized Nov. 14 on Pangutaran Island, about 600 miles south of Manila. He was working for the Texas-based Summer Institute of Linguistics, which translates the Bible into numerous languages.

The Zamboanga Times newspaper said it received the letter today signed by ''Abu Sayyaf, Soldier of Allah'' and postmarked from Jolo Island, where Walton is believed held.

In addition to the removal of foreign Christian missionaries, the group also demanded the ''full and immediate implementation'' of an autonomy agreement for Muslims, the lifting of U.N. sanctions against Libya and the closure of all firms in the south controlled by U.S. business.

The group also refused to recognize any negotiators except those from the United States, Libya, Malaysia, Indonesia, Iran, Iraq and Brunei.

If the demands are not met, the letter said, ''then and only then we will be forced to hang Mr. Walton to death.''

The military had blamed the Abu Sayyaf group for the kidnapping. The Muslim fundamentalist group is led by a Libyan-trained teacher, Abubakar Janjalani, and has been blamed for bombings and killings across the southern Philippines.

No mention was made of any ransom. Earlier today, President Fidel Ramos ruled out paying money to free Walton.

''The government policy is no ransom,'' Ramos said after returning from a two-week visit to the United States. ''The reason for that is obvious. There will be a repetition of similar cases if ransom is granted.''

At least four foreign missionaries - three Spaniards and one American - have been kidnapped in Muslim areas of the south since October 1992. All were eventually released.

About 85 percent of the 65 million Filipinos are nominally Catholic. About 10 percent are Muslim.