On Sunday police said they arrested the man and five co-conspirators and foiled an alleged plot meant to inflict horror.
Police had put the men, aged 18 to 21, under surveillance and made a decision to use their powers of preventive arrest rather than risk an attack, Die Welt reported.
With AP Photos.Berlin police and prosecutors say six people have been detained in connection with what they allege was a plan to carry out an extremist attack on the city's half-marathon.
Berlin Mayor Michael Mueller thanked security forces for preventing an "impending attack with their vigilance and police work".
The half-marathon was being guarded by some 630 police officers, German news agency dpa reported.
The half marathon went off early Sunday without incident amid warm spring sunshine.
In its unsourced report, Die Welt said the main suspect was known to Amri and had planned to stab to death spectators and runners at the half-marathon.
Berlin police tweeted that six people were detained in cooperation with the city's prosecutor's office. Italian police shot and killed the 24-year-old Amri - who had pledged allegiance to the "Islamic State" terrorist group - while he was on the run in Milan. He is said to have possessed two knives that had been specially sharpened on goal.
The other three suspects also had links to Amri, according to Die Welt. No major Islamist attack has been carried out in the country since then.
Still, the German anti-terror apparatus has been bolstered in the last two years.
Political opponents of Chancellor Angela Merkel, including the far-right AfD party, have charged that the security situation has worsened with the arrival of more than 1 million migrants and refugees since 2015, many from African and Middle Eastern conflict hot-spots.