ROME, April 26 (Xinhua) -- An asylum seeker has been arrested on suspicion of plotting a terrorist attack, Italian police announced Thursday.

"A Gambian asylum seeker was arrested in Naples accused of Islamist terrorism. He was plotting an attack," state police tweeted.

The suspect, A. Touray, 21, reached Sicily in March 2017 along with over 600 migrants who had departed from Libya, RAI public broadcaster reported.

He had been staying in a migrant reception center while his asylum claim was being processed. He was arrested on his way out of a mosque after a tip-off from Spanish intelligence services who discovered a video posted on Telegram in which the suspect swore fealty to the so-called Islamic State (IS) terrorist group, according to RAI.

The man told investigators he was asked to commit a terrorist attack by driving a vehicle into a crowd, ANSA news agency reported.

Italy's anti-terrorism policy, which combines surveillance and deportation of suspects before they go into action, has been credited with preventing terrorist attacks.

On April 23, a judge in the northern city of Venice sentenced four Kosovo nationals to prison followed by deportation for plotting to blow up the city's famous Rialto Bridge.

On April 19, the Interior Ministry announced the deportation of a Moroccan national "for reasons of national security".

A total of 271 religious extremists have been expelled from Italy since January 1, 2015, according to the ministry.