A woman cries in front of a picture of dead Jan Palach at the exhibition commemorating this late student in Prague, Czech Republic, Wednesday, Jan. 16, 2019. Palach, a student, set himself on fire in Prague on January 16, 1969 in protest against people's growing lethargy following the August 21, 1968 Soviet-led invasion of Czechoslovakia. He died of fatal burns three days later, aged 20. On January 18, a man set himself on fire in a central Prague square as Czechs marked the 50th anniversary of Palach's self-immolation. (Ondrej/Deml/CTK via AP)

PRAGUE - A man set himself on fire in a central Prague square on Friday as Czechs marked the 50th anniversary of a student's self-immolation in protest at the Soviet invasion that crushed the Prague Spring.

The unidentified man was taken to hospital after bystanders doused the flames that enveloped him in the same spot at the elevated top of historic Wenceslas Square where Jan Palach set himself ablaze in January 1969.

Palach's suicide was a desperate act aimed at lifting the apathy hanging over the country in the wake of the Soviet intervention in August 1968 in which Soviet tanks and troops occupied Prague, snuffing out the Prague Spring process of democratic reforms to the Communist system.

"According to initial information, a man born in 1964 poured an inflammable liquid on his body and set himself on fire," Prague police said on their Twitter feed. An investigation was under way.

Paramedics put the man, who suffered burns over 30 percent of his body, into an induced coma before taking him to hospital, the Prague emergency service said.

There was no immediate word on the man's motives.

"I saw him from the distance, and rushed in as I realised, 'My God, he really is on fire'," said a young woman at the scene next to the National Museum at the head of Wenceslas Square.

"I started to put out the fire, tried to douse it. He had petrol on himself, you can still smell it," she told reporters.