Policemen are seen along a street in central Copenhagen, early February 15, 2015 following shootings at a synagogue in Krystalgade. [Photo/Agencies]

"I saw a masked man running past," said Helle Merete Brix, one of the event's organizers. "I clearly consider this as an attack on Lars Vilks."

Niels Ivar Larsen, one of the speakers at the event, told the TV2 channel he heard someone shouting and firing automatic weapons. "Police returned the fire and I hid behind the bar. I felt surreal, like in a movie," Larsen said.

Visiting the scene of the first shooting, Danish Prime Minister Helle Thorning-Schmidt called it a "political attack and therefore an act of terror."

French President Francois Hollande called the Copenhagen shooting "deplorable" and said Thorning-Schmidt would have the "full solidarity of France in this trial." French Interior Minister Bernard Cazeneuve was arriving Sunday in Copenhagen.

Leaders across Europe condemned the violence and expressed support for Denmark. Sweden's security service said it was sharing information with its Danish counterpart, while U.S. National Security Council spokeswoman Bernadette Meehan said U.S. officials were ready to help with the investigation and have been in touch with their Danish counterparts.

Vilks has faced several attempted attacks and death threats after he depicted the Prophet Muhammad as a dog in 2007. A Pennsylvania woman last year got a 10-year prison term for a plot to kill Vilks. In 2010, two brothers tried to burn down his house in southern Sweden and were imprisoned for attempted arson.