VIENNA, Austria (AP) _ A convicted murderer was returned Thursday to Austria, where he is suspected of killing again after he was freed and began a career as a celebrated writer.

Jack Unterweger, 42, was arrested in Miami Beach, Fla., on Feb. 27 after police caught up with him by tracking his credit card use. Austrian police say they suspect him in the murders of seven prostitutes.

He fled Austria with his 18-year-old girlfriend, Bianca Mrak, on Feb. 14, after police issued a warrant for his arrest in the murders of two of the seven prostitutes.

Unterweger was convicted in Austria in 1976 of murdering a woman and sentenced to life. He was paroled in 1990 after he won critical acclaim for several books about prison life.

He is best known for ''Jail - or In The Name of the Republic.'' Austrian state television filmed a play based on the book last December.

The case sparked a debate in Austrian media over whether criminals should be let out of jail early.

Unterweger's extradition was repeatedly postponed, but U.S. authorities returned him to Austria on Thursday. He arrived at Vienna airport and was transferred to a jail in Graz, authorities said.

Los Angeles police had been investigating whether Unterweger was linked to the murders of three prostitutes there last year. He was in Los Angeles writing free-lance magazine articles on prostitution and street life when the prostitutes were strangled with their bras, police said.

Austrian newspapers reported this week that authorities in Vienna were also investigating whether Unterweger was connected with a prostitute's murder in Prague, Czechoslovakia, in September 1990. Unterweger was in Prague to do research on prostitution, authorities said.