Greek riot police clashed with self-styled anarchist youths in Athens on Wednesday, turning the city centre into a battleground of billowing smoke for hours.
The youths hurled hundreds of petrol bombs at police, burning four cars and one shop. Police retaliated with several rounds of teargas that choked up the capital's streets.
"Five policemen have suffered light burns from the petrol bombs," one police official said.
The clashes started when about 30 youths broke off from an otherwise peaceful march against an education reform law and attacked riot police with petrol bombs.
About 9,000 students, educators and civil servants marched through the city to oppose the law that allows the creation of private universities in Greece, which protesters say will commercialise education and make it hard for the poor to attend college.
The conservative government and main opposition socialists back the bill, saying it will give much-needed competition to Greek state universities and improve higher education.