Hizb ut Tahrir, established in Jerusalem in 1953, has a history of promoting antisemitism and engaging in activities with violent inclinations.
Though much of the world refuses to acknowledge it, there is a worldwide jihad lurking on our doorsteps.
Prosecutors said the two were arrested in the early hours in their homes on Milan's northern outskirts after a two-year investigation.
"We saw it again yesterday in Brussels. All European states are vulnerable, and there is indeed a resurgence of Islamist terrorism," Macron said.
A teacher was killed in a knife attack in Arras, and the investigation was handed to the anti-terrorism prosecutor's office.
No group has claimed responsibility for the blast, which comes amid a surge in attacks claimed by militant groups in Pakistan.
The attacks sparked the NATO-allied US invasion of Afghanistan and Iraq and began the global war on terror.