A rioter throws a stone on July 7, 2017 in Hamburg, northern Germany, where leaders of the world's top economies gather for a G20 summit. (AFP PHOTO/Christof STACHE)

BERLIN, July 11 (Xinhua) -- German Minister of Justice Heiko Maas has pleaded for help from EU partners in the investigation of the violence that rocked Hamburg during the recent G20 summit.

"Many photos and images are currently being assessed to identify the perpetrators. We also rely on assistance from our international partners towards this end," Maas wrote to his European colleagues on Tuesday, the Funke Mediengruppe reported

Masked protestors had clashed with authorities at a series of demonstrations against the G20 summit between Thursday and Sunday last week, throwing Molotov cocktails, setting cars on fire and looting local shops.

More than 20,000 police officers were deployed to ensure safety in the northern German city, hundreds of which were injured.

According to the report, Maas asked other EU justice ministers to treat German requests for legal assistance in connection with the clashes with priority. He also requested that related European arrest warrants issued by Germany would be enforced promptly.

A total of 51 suspects, from Germany, France, Italy, Spain, Russia, the Netherlands, Switzerland and Austria, remain in custody in Hamburg. Hamburg police have established a special commission to prosecute individuals who participated in or helped organize violent protests.