Security services are on high alert for an Islamic State biological weapon atrocity and warn the threat is continent-wide.
They fear deadly gas could be unleashed on public transport or in tourist hotspots like museums and galleries, German newspaper Die Welt reported.
According to the paper, spies have warned European security services of the growing potential for a chemical attack by crazed jihadis.
It is claimed the terrorists are seeking more reliable means of carrying out their barbaric acts following a string of massacres using vehicles and knives.
The claim comes after Australian police foiled an alleged plot to blow up a plane and target a public area using the toxic chemical hydrogen sulfide in July.
This week, Berlin police carried out their third drill of the year to simulate such an attack.
The terror training involved 300 special police units, firefighters and security experts in a three-day operation.
It comes after the head of MI5 warned this week that Britain faces a terror threat on a scale he had never seen before.
Andrew Parker warned there had been a “dramatic” jump in the scale and pace of dangers facing Britain.
He said: “We’ve seen a dramatic up-shift in threat this year.
“Today there is more terrorist activity, it’s coming at us more quickly and it can be harder to detect.”
Twenty UK plots have been foiled over the past four years, including seven in the last seven months.
The UK’s current threat level is “severe”, meaning an attack is highly likely.
That level was raised to critical last month during a bomb attack on the London Underground in Parsons Green.