Authorities initially said the four were Turkish, which has linguistic and ethnic ties with the Uighur homeland of Xinjiang, a region in northwestern China.
The men were arrested Saturday while travelling in a car in Indonesia's Central Sulawesi province, which is home to a network of Indonesian extremists.
National Police spokesman Col. Agus Rianto said Monday that police were investigating them on suspicion of seeking contact with a wanted militant and having possible links to the Islamic State group in Syria.