Indonesian activist Adlun Fiqri could be jailed for wearing a T-shirt allegedly bearing a leftist logo, one of many caught up in a backlash against efforts to shine a light on military-backed, anti-communist massacres half a century ago. Police and the military have in recent weeks rounded up people for allegedly spreading communism -- which remains outlawed in Indonesia -- through logos on T-shirts. They have also seized books about communism and stopped a film screening that touched on the subject. It came after the government last month took timid steps towards making peace with one of the nation's darkest chapters -- the killing of at least 500,000 people in anti-communist massacres in 1965-66, conducted by local groups with military support. The killings began after General Suharto put down a coup attempt blamed on communists. He rose to power on the back of the bloodshed, and went on to lead Indonesia with an iron fist for three decades. During his rule, the massacres were presented as necessary to rid the country of communism -- Indonesia had the world's third-biggest communist party before the killings. Public debate about the killings was taboo, and no one was ever held to account. Since Suharto's 1998 downfall and Indonesia's transformation into a freewheeling democracy, there have been growing calls to re-examine one of the worst mass killings of the 20th century, and even for an official apology. Last month the government took steps towards coming to terms with the episode by backing for the first time public discussions into the killings -- attended by survivors and members of the military -- and they announced they would investigate sites that activists say are mass graves. But the moves swiftly sparked a backlash from the military and police. Conservative elements of the security forces began speaking out against a supposed communist resurgence, despite the fact the Indonesian Communist Party (PKI) was wiped out during the 1960s massacres. "The leftist movement is currently surging in this country," hardline Defence Minister Ryamizard Ryacudu warned in a recent speech to hundreds of retired generals, according to the Jakarta Post newspaper. - 'Surging communist threat' - Observers believe the military is whipping up the spectre of a communist threat as their role in the killings comes under scrutiny. Paul Rowland, an independent Jakarta-based political analyst, said some in the military "would like to revive the communist threat because that effectively justifies the actions that were taken 50 years ago". Those caught up in the backlash potentially face tough punishments, as spreading communist ideology is punishable by up to 12 years in jail. This includes activist Fiqri, 20, who was arrested earlier this month on the eastern island of Ternate for wearing a T-shirt that had a picture of a coffee cup and the letters "PKI" on it, which authorities claim was a reference to the country's former communist party. Police seized more T-shirts and books when they arrested Fiqri and other activists from a group that promotes indigenous people's rights. Fiqri and one other activist are still under investigation. "I think this is ridiculous," Fiqri, who is not currently in custody, told AFP. "It is silly that reading books to gain knowledge and wearing T-shirts can get you arrested." In another case, police arrested and questioned a Jakarta shop owner over the T-shirts he was selling that bore a supposedly communist image of a hammer and sickle. The shop owner insisted it was a picture from the album cover of a German metal band. There have been other reports from across the country of people being detained for wearing T-shirts with hammer and sickle images, and police stopped the screening of a documentary about Buru Island where suspected communist sympathisers were once held prisoner. Security forces have been cracking down on attempts to hold public discussions about the killings since last year, as the country marked the 50th anniversary of the start of the massacres, but the current wave of arrests for promoting communist ideology only began in recent weeks. Authorities have backed the crackdown, with the interior ministry noting a "growing phenomenon" of communism. But for many of Indonesia's younger generation, who are more willing to question the old narrative about the communist killings, the security forces are going over the top. "They are showing excessive paranoia," said Renno Krisna, a 34-year-old music teacher. "It's impossible that communism will make a comeback in Indonesia."