Tunisian authorities from the interior ministry announced the arrests on Saturday, a day after they had been carried out.

According to a statement, the three suspects are part of a "terrorist cell... connected to the terrorist Anis Amri who carried out the terrorist attack in Berlin."

One of the Tunisian suspects is allegedly Amri's nephew.

Amri is believed to have deliberately driven a truck into a Christmas market in a terror attack that killed 12 people and injured 49. He managed to escape on foot.

24-year-old Amri, a Tunisian national, was killed four days after Monday's attack in a shootout with Italian police in Milan. German authorities have come under increasingly intense fire from the public after it emerged that Amri was well-known to security services for his involvement with radical jihadis and was even under surveillance for six months.

His deportation to Tunisia had been approved, but necessary documents from Tunisia were still pending at the time of the attack.

mz/rc (AFP, dpa)