The Abu Sayyaf made the demand in telephone calls to the employers of the men, who were abducted from a barge near Lingkian island off the Malaysian state of Sabah on April 11, said the source, who asked to not be identified.
The three, Sam Walterpel of Indonesia and Malaysians Wong Sien Nung and Toh Chien Tiong, had been manning a barge carrying a cargo of pebbles.
They were later taken to the Cagayan de Tawi-Tawi group of islands near the Philippines’ sea border with Malaysia.
The Malaysian and Philippine governments have said they believed the kidnappers were from the Abu Sayyaf, a Muslim extremist group linked by the United States and the Philippines to the al-Qaeda terror network.
The group is feared for a series of bombings and kidnappings for ransom, mostly targeting foreigners and Christians in the southern Philippines. Regional police commander Isnaji Bantala said officials were hunting the kidnappers.