(MASHHAD, Iran) -- Wearing a head-to-toe black chador, a woman named Parvaneh sat on a park bench waiting for a customer.

Parvaneh knew a killer might find her instead, and that many in Iran might approve.

In the past year, 21 women, all identified as prostitutes and drug addicts and most of them in Parvaneh's home city of Mashhad, have been found dead - strangled with their Islamic scarves which were left wrapped around their necks.

The killings in the city 560 miles northeast of Tehran have forced officials to admit that prostitution is thriving in Iran - a country where clerics rule and talk of sex is discouraged.

Moreover, the suspect arrested for the killings is being applauded by some Iranians.

Saeed Hanaei, arrested July 25, has confessed to killing 16 prostitutes, leaving three unaccounted for, and since his arrest two more strangled bodies have turned up. Police say copycats are at work.

Hanaei lived with his wife and three children in a poor Mashhad neighborhood where prostitutes worked. The 39-year-old construction worker told police he was enraged when his wife was mistaken for a prostitute and propositioned.

``I killed the women for the sake of God, and for the protection of my religion because they were prostitutes and corrupting other people,'' Hanaei told reporters who watched him accompany a a judge to the site where one of the bodies was found.

Prostitution in Mashhad, a holy city with a shrine to the Shiite saint Imam Reza, is especially troubling to Muslims. They blame it on the growing numbers of foreign pilgrims, and on a rapidly growing population of young, unmarried Iranian men.

Some customers consort with prostitutes in the context of ``sigheh,'' or Islamic temporary marriage that can be as short as one hour. ``Sigheh'' has long been banned by the mainstream Arab Sunni sect of Islam, and its practice is limited largely to Shiite Iran, although here too it is regarded by many as abhorrent.

There are Iranians who find prostitution so contemptible that they are praising the alleged murderer.

``God may bless him for killing corrupt women. Killing prostitutes causes fear among them and forces them to stop corrupting our people, especially the youth,'' said Mohammad Taqi Shariatmadaran, a Mashhad man.

Iran's head of judiciary, Ayatollah Mahmoud Hashemi Shahroudi, said that if Islamic laws against prostitution were enforced, the killer would not have been provoked.

But sociologist Mohammad Badizadeh worries that ``the killings may provide enough cause for other people like Hanaei to commit similar murders in the future.''

Mahtab Moradi, strolling with her family in a Mashhad park, said even women like herself who are not prostitutes are afraid.

``The killer has promoted lawlessness,'' she said. ``I can't trust any unknown man any longer.''

One of the women Hanaei confessed to killing is Azam Abdoli, 45, whose body was found shrouded in a black chador on Feb. 11. A convicted drug addict and prostitute, Abdoli had been jailed several times for using drugs.

Abdoli's husband, a street peddler, died in an accident two years ago, according to her 15-year-old daughter, Tayebeh Mohammad Orfani. Tayebeh said her mother had not given up drugs even after her last release from jail last October.

Prostitutes generally use heroin or opium. It costs an estimated 70 cents a day to feed a drug habit in Iran.

Prostitutes have become more cautious and, their price has risen from between $6 and $18 to as much as $25, according to Mohammad, a 22-year-old who said he has been a customer and wouldn't give his full name. A government worker earns about $100 a month.

Mohammad said street prostitutes carry the risk of spreading AIDS, but women working in organized prostitution rings are too pricey - up to $125 for dinner, alcohol, erotic videos and sex in a classy house.

Iran's police chief, Mohammed Baqer Qalibaf, says prostitution ``is a bitter reality in Iran,'' and that ``national will'' is needed to deal with it.

Speaking on state television, he said police could round up the prostitutes within 72 hours but would have nowhere to take them because Iran has no rehabilitation organization for prostitutes.

Parvaneh, who would not give her full name, said she is 32 and charges 100,000 rials, or $12.50 a trick.

``I need money and drugs,'' she said. ``I have to offer my body to earn money and buy what I need.''