Late Tuesday, Rolf Cebin, head of the police department in Duisburg, in western Germany, said, "the removal of the flags was -- in hindsight -- the wrong decision."

Officers entered the unoccupied apartment to remove the flags after demonstrators began pelting them with various things -- some said snowballs were thrown, while others said the demonstrators were throwing rocks.

Fear of violent reaction

The police said they were acting to defuse a situation that threatened to turn violent as over 10,000 people marched through the city in protest at Israel's actions in Gaza.

"Given what I know today, I would have solved the problem in a different way, in order to avoid an escalation," Cebin added.

The ripping-down of the flags sparked furious reaction from Jewish groups. A representative from the Simon-Wiesenthal-Center described the action as "cowardly" and "incomprehensible."

'Would they have torn down a Hamas flag?'

"Can anyone imagine police storming into a privately-owned house to remove a Hamas flag?" the Central Council of Jews in Germany asked?

In a separate incident in Berlin, a 35-year-old man who identified himself as Palestinian attacked a guard outside a synagogue in Berlin with an iron bar.

The man wanted to register a protest against Israel's war in Gaza, a police statement said.