A rolling strike on blocked 14 oil tankers from entering France's biggest oil port of Fos-Lavera, part of the state-run French port of Marseille, according to a Reuters report.
The total number of ships is unchanged on the previous day but down four ships compared with May 2.
"This includes eight crude oil ships and 6 refined oil tankers," the port said in a statement, adding that one gas tanker and three chemical tankers were also blocked from entering the hub.
France's national port union, part of the CGT federation, called on workers last month to stage 24-hour strikes on a weekly basis to protest against government plans to privatise loading activities at state-run ports.
Fos-Lavera, Europe's second-biggest port for oil products, supplies crude to eight refineries in southeast France with a total production capacity of around 800,000 barrels per day.