A German federal court denied prosecutors a detention order for a Syrian man arrested in Berlin this week on suspicion of planning an "Islamic State" (IS)-inspired terror attack, "Der Spiegel" newspaper reported on Friday.

The 27-year-old Ashraf Al-T. remains in detention, however, on charges of falsifying documents.

Quoting the suspect's lawyer, Jonathan Burmeister, "Der Spiegel" newsmagazine reported that after the Federal Court of Justice did not find enough evidence to detain his client on terror charges, investigators obtained an arrest warrant on the lesser charge from a district court.

Burmeister called the procedure against Ashraf Al-T. "a scandal," pointing out that his client had lost his documents in war-torn Syria, which is itself not a crime.

The suspect arrived in Germany in 2015 along with a wave of refugees, thousands of whom entered the country without documentation.

Federal prosecutors and the court have not yet commented on Burmeister's statements.

Planning an attack?

Investigators allege that Ashraf Al-T., whose last name was not given due to privacy laws, was given permission by an IS handler responsible for foreign operations to carry out a terror attack in Germany.

The suspect was arrested on Wednesday in an apartment he was sharing with a refugee volunteer in the Schöneberg district of Germany's capital.

No explosives or other weapons were found.

Germany is on high alert for possible IS-inspired operations since last year's Paris terror attacks, and a series of others that have hit the continent, including in Nice and Brussels.

This week's arrest came after another Syrian man was arrested in October for planning an attack on a Berlin airport. The man hanged himself in his cell in Leipzig after his arrest. Authorities said there is no connection between the two men.

IS claimed responsibility for two attacks carried out in southern Germany in the summer.