Around 800 members of the local Pakistani community were celebrating the birth of the Prophet Mohammed (peace be upon him) with a procession in one of the squares in downtown Athens.
At the same time, supporters of the Thessaloniki PAOK soccer club were in the area, heading for a league game.
The clashes erupted after football fans began insulting and attacking the marchers. Law enforcement officers had to use tear gas and stun grenades to stop the violence, though no arrests were made.
Videos from the scene showed utter mayhem in the street as football fans trampled on Islamic flags, while the Pakistani celebrators tried to defend themselves.
Many Muslims see the Prophet’s birthday as an important time to learn about and reflect on the life of Muhammad, peace and blessings be upon him.
Around the world, celebrations of the Prophet’s birthday include stalls selling Islamic books, leaflets, clothing, prayer mats and other materials.