Thousands of people have joined protests in Athens, Thessaloniki and other Greek cities to commemorate the fatal police shooting of a teenager, hours after violence erupted over a similar incident in the north of the country. Police estimated more than 11,000 protesters had joined protests on Tuesday amid fears of renewed clashes as a Romany boy, shot in the head by an officer, fought for his life. “Stop these murderous policies,” chanted protesters. More than 4,000 law enforcement personnel, backed by heavily armed riot police, were dispatched around Athens. The victim, identified as Kostas Frangoulis, 16, a member of the Roma community in Thessaloniki, was severely wounded as he was pursued by a mechanised police division after allegedly failing to pay a €20 (£17) fuel bill at a petrol station. The incident came on the eve of the anniversary of the death of Alexis Grigoropoulos – a teenager killed in 2008 by an officer in Athens’ Exarchia district – and once again cast a spotlight on the tactics of a police force frequently criticised for its heavy-handedness and brutality. The controversial circumstances of Grigoropoulos’s death unleashed the worst riots in decades nationwide. In a statement, the main opposition leftwing Syriza party said: “History is repeating itself not as farce but as tragedy as a result of police immunity and blatant arbitrariness.” Earlier on Tuesday hundreds of Roma gathered outside a court complex in Greece’s second-biggest city as a 34-year-old officer, who admitted firing his service pistol during the chase, appeared before a prosecutor on charges of attempted manslaughter with possible intent. A police statement said that before the shooting the youth had attempted to “ram police motorbikes” and “repeatedly made dangerous manoeuvres”. In Athens and Thessaloniki, incensed protesters took to the streets late on Monday with banners stating the teenager had been deliberately targeted by police because he was a member of a discriminated minority. In echoes of the unrest that followed the shooting of Grigoropoulos, violence erupted as leftwing and anarchist groups vented their anger, smashing shop windows and hurling rocks and molotov cocktails at police, who retaliated with teargas and stun grenades. In recent years a number of Romany men have been fatally shot or injured in similar chases by police. “It was a murderous attack against a member of a discriminated minority,” said Yiannis Baroutsas, a young student, as he marched through the capital with protesters on Tuesday. “The police have a culture of brutality in this country. They use guns against Roma and stun grenades against us.” Graffiti daubed on public buildings across Athens after Monday’s incident proclaimed: “It wasn’t the gas, it wasn’t money, the cops fired because he was Roma.” The government of the centre-right prime minister, Kyriakos Mitsotakis, has taken what has been described as a draconian approach to law and order with refugees in particular being especially effected by the harsh policies. The Greek leader, hoping for re-election next year, was heavily criticised on Tuesday for electing to announce a €600 bonus for police and coastguard officials on the very day that Frangoulis had been shot. “A lot of us see it as proof that this government condones the tactics of the police,” said Baroutsas, eliciting nods of consent from others on the march. “Couldn’t he have announced the bonus on another day?” A lawyer representing the Frangoulis family described the teenager’s life as “hanging by a thread”, as fury over the incident ran high among Greece’s Roma population. “We don’t want Kostas to become another Alexis,” said the lawyer, Theofilos Alexopoulos. “We want him to make it and to be the cause that will enable us to put all the issues concerning the Roma on the table again.”