Turkish security forces are on the look-out for a T-shirt they believe is linked to the banned Gulen movement and an attempted coup last year.
Over the past 10 days, police have detained nearly 30 people for wearing T-shirts with the word "hero" on them, the CNNTurk news channel reports.
"Some as they were going into an exam, others in university campuses… Almost everyone who wore that T-shirt was confronted by the police," the channel said, adding that arrests were continuing.
The arrests appear to have started after Gokhan Guclu, a former soldier accused of participating in last year's failed coup, attended a court hearing earlier in July wearing the same shirt.
The Turkish government has accused Fethullah Gulen and his Islamist Gulen movement of being behind the July 2016 coup attempt.
The group is now considered a terrorist organisation in Turkey and the T-shirt is being interpreted as a sign of support for the Gulenists and the coup.
The pro-government Sabah newspaper also suggests that, in Turkish, the word hero could be an acronym for the phrase "may the beloved cleric bless", with the word cleric referring to Fethullah Gulen. It says that Gulenists often used such symbols in their communication.
Whatever the reason, the T-shirt in question is no longer available for sale. It was being sold by a popular ready-to-wear clothes chain for 15 Turkish lira ($4.20, £3.20) until the controversy. The company has now withdrawn it, the opposition Cumhuriyet newspaper says.
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