PRAGUE (AP) — A memorial has been unveiled in Prague to honor a Charles University student who burned himself to death to protest the 1968 Soviet-led invasion of what was then Czechoslovakia.

Jan Palach set himself ablaze at Wenceslas Square in Prague on Jan. 16, 1969, almost five months after the armies of five Warsaw Pact countries crushed the liberal reforms known as the Prague Spring. He died three days later.

The brutal crackdown turned Czechoslovakia into a hard-line Communist regime, a political era that ended only after the 1989 Velvet Revolution led by Vaclav Havel.

Two pieces designed by U.S. architect John Hejduk and dedicated to Palach and his mother were unveiled Saturday near the Faculty of Arts where Palach studied. Each is a big cube with spikes representing flames on top.