Unidentified gunmen abducted four men in the Philippines' Maguindanao province, police said on Saturday.
The incident occurred on March 29 but was reported to police only on Friday night, Xinhua news agency quoted the officials as saying.
A senior official said the victims, Jason Cababayao, son of an engineer and owner of J. Trade Concrete Products and Construction Supply in General Santos City, architect Raulito Suyom and Francis Wong and Rho Steven, were stopped by armed men on the national highway in Shariff Aguak town in Maguindanao.
Local radio reports said the kidnappers had already phoned the victims' families and demanded 10 million peso (about $224,000) ransom.
The official said an investigation was on to determine the identities of the perpetrators and locate the four men.