ATHENS, Greece (AP) — Greek authorities are deploying about 2,500 police in Athens to monitor demonstrations marking the 10th anniversary of the fatal police shooting of a teenager that sparked Greece's most extensive riots in decades.

Hundreds of protesters gathered in central Athens and the northern city of Thessaloniki on Thursday for the first of several demonstrations planned to remember Alexis Grigoropoulos, a 15-year-old who died on a night out with friends in the Exarchia district of the capital after being shot by a policeman following an altercation.

The teenager's killing sparked major riots which spread to cities across the country and lasted for weeks.

The policeman was convicted of murder and sentenced to life in prison. The second policeman present was sentenced to 10 years and was granted conditional release several years ago.