Berlin
BerlinFlash 90

Six people were detained on Sunday in connection with what police and prosecutors allege was a plan to carry out an attack on Berlin's half-marathon, German authorities said, according to The Associated Press.

"There were isolated indications that those arrested, aged between 18 and 21 years, were participating in the preparation of a crime in connection with this event," prosecutors and police wrote in a joint statement.

Berlin police tweeted that six people were detained in cooperation with the city's prosecutor's office.

The German daily Die Welt first reported that police foiled a plot to attack race spectators and participants with knives.

The main suspect allegedly knew Anis Amri, the Tunisian terrorist who killed 12 people and injured dozens more when he drove a truck into a Christmas market in Berlin in December of 2016.

Amri was killed during a shootout with Italian forces in Milan, four days after the deadly terrorist attack in Berlin.

One of the apartments Berlin police raided before the race started Sunday was also searched after the Christmas market attack, Die Welt said.

Die Welt reported that the main suspect, who was not identified, had prepared two knives to use in the attack. It also wrote that in one of the searched apartments, dogs trained to find explosives barked when they were taken into the dwelling's basement.

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.