Morocco, a Western ally against militancy, often announces it has broken up militant cells accused of plotting attacks inside and outside the kingdom.
The suspected Italian militant, who lives in Belgium, was arrested on June 8 when landing in the eastern city of Oujda, based on intelligence showing that he had ties to the Islamic State group and was involved in a plan to attack targets in Morocco, the statement said.
In 2014, he tried to travel to Syria or Iraq but failed, despite guidance from an Islamic State member, and returned to Belgium, the statement said.
Authorities said the suspect has already visited Morocco in 2015, sent by Islamic State, and identified targets in Casablanca, Morocco's biggest city.
Moroccan security officials provide information that help their European counterparts in fighting militancy, especially during the recent Paris attacks.
Thousands of fighters from Morocco and other Maghreb nations, such as Tunisia, have joined militant forces in the conflict in Iraq and Syria, and also in Libya.
Some are threatening to return home to carry out attacks and recruit more militants, security experts say.
Moroccan officials estimate that 2,000 Moroccan fighters have joined armed groups in Syria and Iraq, including Islamic State and the al-Qaeda linked Nusra Front, and about 200 have been jailed on their return home.
The North African state has suffered bomb attacks by suspected Islamist fighters, most recently in 2011 in Marrakesh.