Khan Younis, Gaza Strip - A note stuck to the door of Mohammed al-Shaer's tiny music shop warned him several months ago that selling tapes and CDs of popular Arabic music was "haram," or forbidden by Islam.
He paid no heed until a bomb went off outside his business this week -- apparently the work of what Palestinian security officials now suspect may be a secret "vice squad" of Muslim militants.
"If they cared about their religion, they would (instead) stop people from killing each other," Al-Shaer, 19, said angrily.
In recent months, about three dozen Internet cafes, music shops and even pharmacies have been attacked, with assailants detonating small bombs outside businesses at night, causing damage but no injuries.
The bombings started in October, a new phenomenon even in violent Gaza, where more than 130 people have been killed in factional fighting between Hamas and Fatah in recent months. The attacks could point to a further spread of religious extremism in Gaza, where poverty and lawlessness have been on the rise.
There has been no credible claim of responsibility for the attacks, police said.
Police initially believed the attacks were part of local business disputes but increasingly came to suspect an orchestrated campaign by religious extremists, said one law enforcement official, speaking on condition of anonymity because of the sensitive nature of the subject.
There have been no arrests, but Gaza police spokesman Ramzi Shaheen noted that the method of operations was the same in all cases. "We can't exactly say who is behind this, but the repeated nature of the attacks leads us to certain conclusions," he said, without elaborating.
In the town of Rafah on the Gaza-Egypt border last week, a huge bomb wrecked a pool hall in a building owned by Ramzi Abu Hilao, blowing out the front wall and littering the interior with metal scraps. He said there was no warning before the blast.
"I received a written message after the bombing from a group called 'The Swords of Truth' that began with a verse from the Quran and said they wanted to correct the bad behavior in Palestinian society," he said.
In deeply conservative Gaza, devout Muslims would consider Internet cafes to be dens of vice because young men are known to view pornography there. Music shops could be a target because some believers fear pop music distracts from prayers. The targeting of pharmacies remains a mystery, though, officials say.
Fears of an Islamic cultural crackdown have risen since the Islamic Hamas took over the government a year ago after winning an election. On Monday, Education Ministry officials said they removed an anthology of folk tales from school libraries because of explicit sexual language, destroying 1,500 books.
Entertainment in Gaza is extremely limited -- there are no movie houses or theaters. Surfing the Net and listening to music are among the only outlets for the young, and hundreds of small Internet cafes and music shops operate across Gaza, some even near mosques.
Several music shops in Khan Younis, in southern Gaza, have received warnings in recent months not to sell pop music.
Khamis Abdeen, 20, said he removed most tapes and CDs but left several dozen tapes with the latest songs on the shelves of his family's shop, hoping he could sell them quickly. At the beginning of the year, the shop was attacked, damaging $5,000 worth of merchandise, he said. Abdeen has stopped selling tapes.
In Gaza City, Shawki Abdel Karim, 39, said he recently blocked access to adult Web sites on the 24 computers in his Internet cafe, but he can do little else to stop attacks. The cafe is separated by gender -- girls upstairs, boys downstairs.
"After I go home, all I can say is to pray to God to protect my place," he said.
The bombings are the latest sign of a society buckling under the pressure of more than six years of fighting with Israel, internal strife and deep-rooted poverty, said Anwar Wadi, a psychologist at the Gaza Community Mental Health Center.
"This is a poisoned society," he said. "Since Israel withdrew from the Gaza Strip (in 2005), hidden problems have come to the surface."
Shaheen, the police spokesman, said solving problems by violence has become the norm.
"Everybody has guns. There's no rule of law," he said. "We've reached a stage where a person is a hero by how he can break the law."