Wave of protests after Greek 'neo-Nazi' killing
Anti-fascist protesters have held demonstrations across Greece following the killing of a left-wing activist by a suspected neo-Nazi.
In some cities police fired tear gas to keep the protesters at bay.
A 45-year-old man has allegedly confessed to stabbing Pavlos Fyssas. The suspect is a supporter of far-right party Golden Dawn, which is blamed for a tide of attacks on immigrants.
Greece's deputy PM said it must now be treated as a "criminal organisation".
Evangelos Venizelos, who is the head of the Pasok socialist party, the junior party in the coalition government, said Golden Dawn had "violence as its priority".
He and Prime Minister Antonis Samaras have agreed to use all available legal powers to crack down on the movement, Greek daily Kathimerini reports.
Golden Dawn has denied any connection with the killing and has turned on its accusers, calling them "miserable and wretched not only because of their brazen lies and slander but because they are exploiting a tragic event for politicking, to win votes and to divide Greek society".
The dead man was Pavlos Fyssas, 34, a rapper who went by the name Killah P.
He was stabbed twice in the heart and chest on Tuesday night in a brawl, after he and friends had been watching a football match in a cafe in Keratsini, a suburb of Athens.
Some witnesses said he and his friends were chased by a mob before he was stabbed.
He is due to be buried on Thursday morning.
Thousands of people rallied on Wednesday at the spot where he was killed.
Violence broke out in the evening, when youths set fire to rubbish bins, broke up paving stones and threw pieces at police, who fired volleys of tear gas. At least 23 people were arrested.
There were also clashes at demonstrations in the cities of Thessaloniki and Patras.
The murder suspect appeared before prosecutors on Wednesday evening, along with his wife, who is accused of concealing evidence. He reportedly told police he was a supporter of Golden Dawn.
The party denies being a neo-Nazi movement, though its badge resembles a swastika, some senior members have praised Adolf Hitler, and its members wear black t-shirts and combat trousers at anti-immigrant demonstrations.
It came from nowhere to win nearly 7% of the vote in 2012 general elections and took its place in parliament. Opinion polls suggest its support has risen still higher.
A number of reports, including some gathered by the BBC, have suggested there are strong ties between Golden Dawn and elements of the Greek police.
Greece's Public Order Minister Nikos Dendias said he was "shaken" by the stabbing, and cancelled a visit to Rome scheduled for Thursday.
He said a number of recent violent incidents "show in the clearest possible way the intentions of the neo-Nazi creation".
Golden Dawn leader Nicholas Michaloliakos said his party "unreservedly condemns the murder of the 34-year-old at Keratsini and denies any involvement of the party".
He suggested it was a coincidence that the alleged perpetrator was a party supporter.