Four suspected "Islamic State" (IS) sympathizers were detained by Italian police during a "vast anti-terrorism operation" in northern Italy on Thursday, according to authorities.

Investigators intercepted an IS communication which ordered one of the suspects, a Moroccan-born man, to carry out attacks in Italy "with particular attention to the city of Rome," Milan prosecutor Maurizio Romanelli told reporters.

The communication specifically focused on the Holy Year pilgrimage which is currently underway.

"This is a new profile, because it was not a generic indication, but an indication given to a specific person who was invited to act within the territory of the Italian state," Romanelli said.

Those arrested "had very bad intentions," Interior Minister Angelino Alfano told the Mattino 5 news program.

Multiple arrests

Earlier on Thursday, Italian authorities issued arrest warrants for six suspects, four of whom were arrested during the anti-terrorism operation.

The suspect who received the direct IS order was identified as Abderrahim Moutahrrick. He was arrested along with his wife, Salma Bencharki, who were allegedly planning on traveling to IS territory along with their 2 and 3-year old children. Romanelli added that Moutahrrick had taken Italian citizenship and was known as an accomplished boxer.

Another Moroccan-born man, identified as Abderrahmane Khachia, was also arrested in Varese. He reportedly planned on traveling with the couple to become a foreign fighter. His brother was expelled from Italy in January 2015 on international terrorism charges.

Two arrest warrants still stand for Mohamed Koraichi and his wife, who left Italy to join IS last year with their three small children. According to Romanelli, Koraichi became an Islamic State fighter and communicated the attack orders to Moutahrrick.

The fourth arrest was Koraichi's sister, who put her brother in contact with the three others arrested on Thursday.

The prosecutor added that there was no indication that there were any imminent attacks, and said authorities worked quickly to conclude the investigation.

rs/jm (AP, dpa, Reuters)