The official Iran daily on Wednesday said the man, identified only as Mahdi, was arrested two months back and is being held in Tehran's Evin prison.
He is presumed to be Mahdi Tayyib, 50, who was quoted as telling a Tehran judge he contracted HIV from a Swedish woman in Paris in the early 1990s and later moved to Sweden.
Stockholm police spokeswoman Stina Wessling said her office had not been informed of the arrest.
"Perhaps he was arrested in Iran for another crime, in which case they would get to us later on," she said.
The newspaper cited Swedish sources as saying Tayyib had unprotected sex with 140 women there between 1993 and 1998, with 20 to 25 of them having been drugged and raped. He allegedly also had sex with men.
The paper said Tayyib also had sex with a number of Iranian women students, and published his photograph with a plea from investigators for "anyone having complaints against him to contact the prosecutor's office".
According to Swedish press reports, Tayyib had been in Miami, Florida when he assumed the identity of a man named James Kimball, who died in March 1985.
He moved in 1992 to Sweden, where he obtained a residence permit in 1993 and was officially registered as having no income.
'Date rape' drug
America's Most Wanted website said Tayyib was known to go to discotheques on a nightly basis to pick up women.
HIV carrier allegedly drugged and
raped 20-25 victims
It cited officials as saying that on the nights he did not meet a willing candidate he would use the "date rape" drug Rohypnol to incapacitate his victims and then rape them.
Iran quoted Tayyib as telling a Tehran judge he had been jailed in the United States for six months in 1985 for assaulting a woman in a disco.
"After my release, I paid $500 for the passport of a dead American named James Kimball and then I went to France. In 1991, I found out I had AIDS, which a Swedish woman had given me," he said.
The newspaper quoted him as saying he returned to the US, where he met a Swedish woman who followed him to Sweden.
"I lived in Sweden for six years and, in 1998, when I found out the police were looking for me, I left Sweden using the passport of my friend, Muhammad Maruz. I took a ship for Denmark, and then a train through Germany and the Netherlands. I then took an aeroplane to Istanbul, where I paid $250 to be smuggled into Iran," Tayyib said.
Iranian investigators were quoted as saying Tayyib is fluent in English, French, Swedish and Turkish, and had deceived a number of Iranian girls, promising to marry them.
In Iran, he variably passed himself off as either an American or a Canadian, and used the names James and Robert, the investigators said.
Iranian investigating magistrate Sayyid Muhammad Tabatabai-Nijad said that "despite his being HIV positive, he managed to stay in good shape, taking six different types of medication and doing a lot of sports. He looked good".