The man wanted for the Berlin lorry attack that killed 12 people and injured 49 had been under surveillance earlier this year according to media report.
Anis Amri, 23, was reportedly monitored on suspicion of planning a robbery in order to pay for guns but that surveillance was lifted for lack of evidence.
Prior to entering Germany, Anis Amri had served four years in Italy for arson and also faced a jail sentence in absentia in Tunisia.
The failed asylum seeker is now the subject of a manhunt across Europe for the attack that happened in Berlin, Germany.
An arrest warrant has been issued after his residence permit was found in a car that left a trail of carnage at a Christmas market near the Kurfuerstendamm, on Monday evening.
German authorities have warned he could be armed and therefore dangerous. They are offering a reward of up to €100,000 (£84,000; $104,000) for information leading to the arrest of Anis Amri.