Union workers in the Italian port city of Genoa refused to load two generators aboard the Bahri Yanbu vessel on Monday, saying that the weapons on the Saudi ship contravened a United Nations treaty and might be used against civilians in Yemen.
"We will not be complicit in what is happening in Yemen," union leaders said in a statement, with port officials confirming that the generators were blocked on the quay.
Some protesters and human rights activists also gathered at the port, carrying banners that read, "No to war."
Earlier this month, the Bahri Yanbu vessel loaded arms in the Belgian city of Antwerp but was prevented from picking up another consignment of weapons in the French port of Le Havre following protests by humanitarian groups.
The move was prompted after the investigative website Disclose published leaked documents that showed Saudi Arabia was using French weapons including tanks and laser-guided missile systems, against civilians in Yemen's war.
Faced with Growing criticism, French President Emmanuel Macron admitted that the weapons were indeed being used in the war but only within Saudi Arabia's border.
Amnesty International condemned France's weapons sales to Saudi Arabia, saying Paris cannot be trusted on claims that the weapons are not being used against civilians.
Describing the move as "a clear hypocrisy to evade crimes", Yemen's Houthi Ansarullah movement also lashed out at the French government for supplying Saudi Arabia and the United Arab Emirates (UAE) weapons that have been used in their war on the impoverished country.
One of the main arms suppliers of Saudi Arabia, Paris has faced increasing pressure to review its sales to the oil rich kingdom.
Saudi Arabia and a number of its regional allies launched a devastating campaign against Yemen in March 2015, with the goal of bringing the government of former President Abd Rabbuh Mansur Hadi back to power and crushing the Houthi Ansarullah movement.
Ever since its onset in March 2015, the Saudi-led war has killed tens of thousands of Yemeni civilians and plunged the country deep into what the UN calls worst humanitarian crisis in the world today.