Mindanao, Philippines - A second suspect in the Philippines kidnapping of an American man who police say was likely killed by his captors has been arrested, police said Thursday.

Elliot Eastman was snatched from his home on the southern island of Mindanao on October 17 last year, and police subsequently said his kidnappers shot him dead that day when he tried to escape.

Jakaria Jamani, a resident of the Mindanao municipality of Sibuco, was arrested at sea on Tuesday and is being held without bail while awaiting trial for the kidnapping, a police statement said.

The statement described him as the "mastermind/planner" of the abduction.

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Another suspect, arrested in November, has told police Eastman was dead.

Last month, police told AFP a relative of one of the suspects reported the kidnappers threw the American's body into the sea. It has never been recovered.

The US embassy in Manila has declined to comment on developments in the case, referring queries to Filipino authorities.

Mindanao was wracked for decades by kidnappings for ransom, but incidents have waned in recent years.

Police said the suspects in the Eastman abduction were not thought to be affiliated with kidnap gangs from previous years, and their motive remains unknown.