ROME (AFP) - Italian police have arrested a Moroccan man suspected of taking part in the attack on the Bardo National Museum in Tunis in which 21 tourists were killed in March.

"A Moroccan national, wanted internationally, was arrested yesterday evening in a town in the Milan region. The Tunisian authorities suspect him of having taken part in the Bardo attack," a police spokesman told AFP on Wednesday.

The arrest was made by Italy's anti-terrorism DIGOS police. Milan's prefecture was expected to provide more details at a press conference later in the day.

The Italian press reported that the Moroccan was 22 years old and was arrested in the town of Gaggiano in northern Italy, some 13 kilometres from the country's economic capital.

The Bardo attack on March 18 killed 22 people in total, including a Tunisian policeman.

Two Tunisian assailants who had shot tourists as they got off buses outside the museum were gunned down at the scene after taking hostages inside the museum.

Tunisia's President Beji Caid Essebsi said a few days after the attack that a third gunman was on the run.