A weekly rally by a German group protesting what it calls "the Islamization of the West" was called off on Sunday because of a terrorist threat against one of its organizers, the group and authorities said.

The group calling itself PEGIDA, or Patriotic Europeans against the Islamization of the West, has organized rallies every Monday in the eastern German city of Dresden. Last week's event drew the biggest crowd yet, with police estimating some 25,000 people attended.

PEGIDA said on its Facebook page that this Monday's rally was called off for security reasons because, according to police, "there is a concrete threat against a member of the organization team."

Dresden police chief Dieter Kroll said in a statement that there was a "concrete" threat connected to a member of the PEGIDA team and Monday's demonstration. In view of that, he issued an order barring any rallies in the city on Monday.

Kroll said there had been a call for attackers to mingle with the demonstrators and kill one of the protest organizers. He didn't specify where the threat came from, or if any group was behind it, but said it resembled an Arabic-language Tweet describing PEGIDA as an "enemy of Islam."

He said there was no information about any specific potential attacker or how exactly an attack might be carried out, which led officials to conclude that there was no way to prevent possible danger other than canceling the rally.

The move comes amid heightened security concerns across Europe following last week's terror attacks in Paris, in which 17 people were killed.

PEGIDA called on supporters to instead hang flags out of their windows and light candles on Monday evening. It said the group and authorities were working on a "security concept" for its next rally on Jan. 26.

The Dresden rallies have drawn criticism from many German politicians. Similar groups in other German cities haven't drawn anywhere near as much support, and there have been much larger demonstrations against them.