Italian trade unions announced a nationwide strike on Friday to protest Israel’s attack on the international “Freedom Flotilla” heading to Gaza, and to show solidarity with the passengers detained by Israeli forces.

The Italian General Confederation of Labour (CGIL), the country’s largest labor union, said in a statement that the strike is being held “in solidarity with Gaza and the Freedom Flotilla, and in defense of constitutional values.”

The union added that the assault on civilian ships carrying Italian nationals constitutes “an extremely serious incident.”

Several Italian cities witnessed demonstrations and protest marches late Wednesday in response to the Israeli raid in international waters.