Greek magistrates on Friday began questioning dozens of suspects over the fatal stabbing of a football fan near Athens ahead of a Champions League game this week.
A 29-year-old man, Michalis Katsouris, died after a brawl on Monday between hardline supporters of Greek side AEK Athens and Croatian club Dinamo Zagreb.
In light of the tragedy, UEFA postponed Tuesday's third-round qualifier between the two sides until August 19.
Police made around 100 arrests -- the majority said to be linked to Dinamo's extremist 'Bad Blue Boys' supporters, a police source said.
Three judges are conducting the interviews, which are expected to be completed by Sunday night, local media reported.
Of the group of 30 grilled on Friday, a dozen -- 10 Croatians, an Albanian and a Greek -- were remanded in custody, Greek news agency ANA reported.
Greek Prime Minister Kyriakos Mitsotakis and UEFA president Aleksander Ceferin "spoke on the matter by telephone" on Friday, authorities in Athens said.
The pair will meet in Athens on Wednesday to discuss "what is happening in Greek and European football", the statement added.
Ceferin, Mitsotakis and other Greek government ministers will then hold a meeting with the owners of Greece's four big clubs -- AEK, Olympiakos, Panathinaikos and PAOK.
On Tuesday, the Greek minister for citizen protection suspended seven police officers for not ensuring adequate security measures to prevent the brawl.
The death of Katsouris caused shock in a country that has seen several incidents of violence erupting at football matches.
Last year, teenager Alkis Kampanos was fatally stabbed in a fight in the northern city of Thessaloniki between supporters of the city's rival clubs, Aris Thessaloniki and PAOK.
The government subsequently increased the maximum sentence for fan violence from six months to five years.
Last month, seven defendants were found guilty of Kampanos's murder and handed life terms. Five others were jailed for complicity.
Police meanwhile have beefed up border security in the wake of this week's killing.
Supporters of AEK and Dinamo have been banned from travelling abroad for the clubs' two forthcoming encounters -- the qualifier in Athens on August 19, and the second leg in Zagreb next Tuesday.
On Thursday, seven Romanian fans were arrested on the border between Greece and Bulgaria in possession of two knives.
They were given one-year suspended prison terms on Friday and each fined 1,000 euros ($1,095), a police source reported.
According to police, the supporters were on their way to Thursday's Champions League qualifier between Olympiakos and Belgian side Genk.
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