The announcement by prosecutors came after the arrest on Tuesday of a 20-year-old Syrian who has been living in Germany since 2015 and has in the past served time in prison for crimes of violence.

In the attack on two German visitors in Dresden’s Old Town on October 4, a 55-year-old man was fatally injured, while his 53-year-old male companion survived. Their attacker was able to flee.

Prosecutors said they were investigating charges of murder, attempted murder and causing grievous bodily harm.

In an indication of the seriousness with which the attack is being taken, federal prosecutors announced they were taking over the case.

In November 2018, a Dresden court found the suspect guilty of recruiting for a foreign terrorist organization, acquiring the means for committing a serious crime threatening state security, causing injury and making threats.

Following a subsequent case in Leipzig for an attack on a law enforcement officer, he was sentenced to a total of two years and nine months as a youth offender, being released from prison under supervision on September 29 this year.

According to information received by dpa, the suspect has been under surveillance as a supporter of Islamic State since August 2017 and is seen by the authorities as a potential threat.

He is in possession of papers allowing him to remain in Germany but has not been granted asylum.