An Iranian man has been arrested in western Germany suspected of preparing an "Islamist attack" using cyanide and ricin, police and prosecutors said Sunday.

The 32-year-old man was "suspected of having prepared a serious act of violence threatening the security of the state by obtaining cyanide and ricin with a view to committing an Islamist attack", police in Muenster and Recklinghausen, along with the Duesseldorf prosecutors' office said in a statement.

But a search of the man's residence in the town of Castrop-Rauxel found no evidence of toxic substances, Duesseldorf prosecutor Holger Heming told AFP.

Authorities had been given a "serious tip" that had prompted the overnight raid, regional interior minister in North Rhine-Westphalia, Herbert Reul said.

The arrest was carried out shortly before midnight on Saturday evening, a spokeswoman for the police said.

Another person, thought to be the main suspect's brother, was also taken into custody during the operation, she said.

Whether the second man was implicated in the allegations was being examined, chief prosecutor Heming said.

Authorities would "decide at a later point" whether the 32-year-old main suspect would be presented before a judge, police said.

The raids were carried out by agents wearing protective suits against the perceived chemical hazard, according to local media reports.

German authorities were tipped off to the risk of an attack with a "chemical bomb" several days ago by a foreign intelligence service, the German daily Bild reported.

Ricin is a highly toxic substance, which is classed as a "chemical weapon" in Germany. Much like cyanide, ricin can be lethal.

In 2018, a Tunisian man and his wife were arrested on suspicion of planning a biological bomb attack in Germany.

The couple, who sympathised with the Islamic State group, were found in possession of 84 milligrams of ricin in their Cologne apartment. The man was sentenced to 10 years in prison in 2020, while his wife received an eight-year sentence.

Germany has been targeted in recent years by several Islamist attacks, including a 2016 truck attack on a Christmas market, that killed 12 people and left dozens injured.

A 13th victim died five years later having suffered serious injuries in the assault.