Tunisian authorities have arrested the nephew of the Berlin Christmas market attacker Anis Amri. The man is reportedly one of three men arrested by the Tunisian Interior Ministry on Saturday (24 December).

All three are suspected of belonging to a terrorist cell, but links to the attack in Berlin on 20 December are yet to be confirmed.

Amri allegedly communicated with his nephew on the Telegram messaging app and sent him money to join him in Europe. The money was said to have been sent through a third party for the nephew to join the Abu al-Wala cell in Germany.

He also is said to have asked his nephew to pledge allegiance to Islamic State (Isis).

A statement from the Tunisian Interior Ministry said: "It turns out that among the members of the cell, the nephew of the Berlin terrorist confessed that he communicated with his uncle through the Telegram app to escape security surveillance, as it encrypted and secret. [Amri] asked [the nephew] to swear allegiance to the Daesh terrorist organisation."

According to the Independent, the nephew is an 18-year-old named "Fredi". He was arrested in Amri's hometown of Oueslatia, reported the Guardian, whereas the others were arrested in Tunis.

The arrests come days after Tunisian-born Amri drove a truck into a crowded Christmas market in the centre of Berlin. The attack, near the Kaiser Wilhelm memorial church, killed 12 and injured 48.

Amri then went on the run until he was tracked down by Italian police in Milan. Italian interior minister Marco Minnitti said Amri was behaving suspiciously and was stopped by a routine police patrol.

According to Italian police, Amri then pulled a gun from his backpack, shouted "God is greatest" in Arabic and opened fire, injuring an officer. A second policeman with only nine months' service returned fire, killing him.

Berlin's Breitscheidplatz Christmas market has since reopened to the public, but with added security. Mourners and well-wishers have laid flowers, lit candles and left tributes to the victims at the site.