HARTFORD, Conn. (AP) _ The reputed former head of the Colombo organized crime family in New York City has been arrested seven years after he went underground rather than face sentencing on an extortion conviction.

Alphonse ''Allie Boy'' Persico, who had been on the FBI's 10 most-wanted list, was arrested Monday by the U.S. Marshal Service at a West Hartford apartment, U.S. Attorney Stanley Twardy said.

Persico had been a fugitive since June 20, 1980, when he defaulted on $250,000 bond and failed to appear for sentencing in New York. He faced up to 20 years each on three counts of extortion in connection with loan-sharking activity.

The Marshal Service said seven deputy marshals followed a trail of phony identification and aliases to the apartment, where Persico had $7,000 in cash in his possession when he was arrested.

Marshals had not staked out the apartment before Monday but ''just went to the location and hit pay dirt,'' said U.S. Marshal Charles Healey in New York.

Authorities had been following Persico's trail for years, Healey said today.

''The last seven years basically we have been getting anonymous tips,'' he said. ''They were taking us all over the world - tips that he was in Honolulu, Japan, Miami, South America. They were numerous but they never panned out.''

Quoting a source close to the investigation, The Hartford Courant reported in today's editions that Persico had been living at various locations, including the West Hartford apartment, which was rented by a woman. Justice Department officials would not identify the woman or say if she would be charged.

Laura Brevetti, assistant attorney-in-charge at the Justice Department's organized crime strike force offices in New York City, identified Persico, 57, as the reputed head of the Colombo family before fleeing, and said Persico's brother, Carmine, took over in his place.

Persico's criminal record dates back to 1949 with charges of assault, murder, fraud, false statements on bank loans, firearms violations, extortion and possession of stolen property. He also served 17 years of a 20-year sentence on a murder conviction.

Considered armed and dangerous, Persico had been known to travel with armed guards.