A knife attack that killed one tourist and seriously injured another in the German city of Dresden in early October is being treated as a terrorist attack, prosecutors said Wednesday, according to AFP.

A 20-year-old Syrian man was arrested on Tuesday evening and is believed to have an Islamist background, federal prosecutors in the city of Karlsruhe said

The suspect allegedly attacked the two tourists, who had travelled together from North Rhine-Westphalia, on October 4.

One of them, a 55-year-old man, later died from his injuries in hospital. The other, aged 53, survived with serious injuries.

"This act once again demonstrates the danger of Islamist violence," Interior Minister Horst Seehofer said in a statement on Wednesday.

"Whatever the form of extremism and terrorism, the utmost vigilance is called for," he added.

The suspect has a long criminal record including charges of soliciting support for a foreign terrorist organization, obtaining instructions to commit a serious act of violence endangering the state, bodily injury and threats.

He came to Germany in 2015 along with hundreds of thousands of Syrian migrants and had become increasingly radicalized since 2017, when police classified him as dangerous, according to a report in Der Spiegel.

He had been living in Germany under "tolerated" status granted to people whose asylum requests have been rejected, but who cannot be deported and had been released from a juvenile detention center on September 29, German media reported.

Police and the public prosecutor's office in Dresden said the examination of evidence had led to the Syrian man and "raised the question of an Islamist attack".

Responding to the news on Twitter, Justice Minister Christine Lambrecht said "Islamist terror is an ongoing major threat to our society, which we must fight against with all our might."

Germany has been on a high level of alert due to a series of terrorist attacks in the country in recent years.

In one attack, a 17-year-old Afghani with an axe attacked passengers on a train in Wurzburg before being shot dead by security forces.

In a second incident, an attacker set off a bomb in a restaurant in Ansbach, killing himself and wounding 12 others.

The worst such attack took place in December of 2016, when Tunisian terrorist Anis Amri killed 12 people and injured dozens more when he drove a truck into a Christmas market in Berlin.

Earlier this year, a German court sentenced a 31-year-old Tunisian to 10 years in prison for planning a biological bomb attack with the deadly poison ricin.