Police launched raids on addresses across Germany overnight on Tuesday, arresting six Syrian men suspected of plotting a mass casualty terror attack with “weapons or explosives” in the country.

Around 500 police officers took part in the raids on eight addresses in four states, taking six Syrian men aged between 20 and 28 years old into custody, as well as seizing mobile phones, computers, and paperwork.

According to the Frankfurt attorney general, the arrested men are supporters of Islamic State and are suspected of having planned a”serious state-damaging act of violence” with “weapons or explosives on a public target”, reports German broadsheet Die Welt.

The men are thought to have travelled to Europe under false identities, posing as refugees — but were actually terror fighters.

Two of the men entered Germany as asylum seekers in 2014, while another two came in 2015, and police were alerted to their extreme views by other migrants.

While German media has stopped short of reporting the suspected target of the terror plot, British newspaper Daily Mail cites reports that the men intended to launch their attack against a Christmas market — meaning the plot could have been foiled with just days or weeks to spare.

The arrests come little less than a year after a successful attack on German soil against a Christmas market by Tunisian asylum seeker Anis Amri, who drove a hijacked lorry into a Christmas market, killing 12 — including the Polish truck driver who Amri killed while stealing the vehicle.

Merkel Ally: Christmas Market Attack Suspect 'Should Not Have Been in Germany in the First Place' https://t.co/nansiKcsau pic.twitter.com/fzPW9qfCJR — Breitbart London (@BreitbartLondon) December 23, 2016

After the fatal attack — and the shooting of the killer by Italian police after he was able to flee Germany — it has been revealed that German police missed multiple opportunities to arrest and deport Amri, but failed to do so. Breitbart London reported that a Syrian asylum seeker who was a roommate to the terrorist had warned authorities of his extreme views, but no action was taken.

The killer was already well known to police before his attack, yet his known drug dealing was not used as a pretext to deport him when the opportunity was available.

Following the attack, Christmas markets across Europe were placed under heavy security with rifle-carrying police officers patrolling between heavy concrete barriers, deployed to prevent the unwanted incursion of vehicles into the spaces.

As Christmas markets again open across Europe in anticipation of the 2017 season, armed patrols and anti-vehicle attack measures can again be seen in force, one of the many visible outward signs of how the number of recent terror attacks have impacted and changed everyday life in Western Europe.