A self-professed "hit man" who claims that an aide to Philippine President Ferdinand Marcos ordered him to kill opposition leader Benigno Aquino Jr., who was fatally shot in Manila in August 1983, has been arrested here and faces deportation.

Jose Fronda Santos, who has been in the United States illegally since his 60-day tourist visa expired last spring, was arrested March 1 and is being held in the Oakland jail. He has said he did not obey the order to kill Aquino.

Los Angeles police said Santos came to their attention through his association with Robert Cabrera, a Filipino arrested today in a year-long police "sting" operation.

Los Angeles police Cmdr. William Booth said Santos "has the reputation" in the Philippines "of a very, very violent person. We also learned the INS Immigration and Naturalization Service had a warrant for his arrest, so we just thought it would be better to take him off the streets."

Santos, who once was a security guard for Aquino, testified here last year before a congressional committee and a Filipine commission investigating Aquino's murder at the Manila airport. Santos, who claims to have killed more than 50 people, said that Brig. Gen. Luther Custodio, chief of airport security, told him to murder Aquino, and that the order came from Marcos.

Custodio, who has denied Santos' allegations, is being held in the Philippines, charged with conspiracy in Aquino's murder.

Santos is fighting deportation, saying he fears "certain death" if he is returned to the Philippines.