Workers at a major Israeli seaport in the southern city of Ashdod suspended operations on Tuesday following heavy rocket fire from the nearby Gaza Strip.
Violence has flared in recent days across the Israel-Gaza border, and the Israeli military said on Tuesday its Iron Dome defense system shot down four Palestinian rockets in the skies above Ashdod, about 25 km (15 miles) up the coast from Gaza.
The Ashdod port, which is notorious for labor unrest, said in a statement that the head of the labor union instructed workers to leave their posts "without permission and without letting anyone know".
A spokesman said the piers were completely shut down and the port called on workers to return to their jobs.
Israel's Globes financial newspaper said on its website the walkout might also be related to a dispute with management.
Nearly all of Israel's trade passes through its two Mediterranean ports at Ashdod and Haifa, which is further north. While both have powerful unions, Ashdod in particular has seen a large amount of workers' strikes in recent years.
Reporting by Ari Rabinovitch