Rhine river traffic was disrupted on Thursday as workers protesting against a planned French pensions reform staged a strike at a waterway lock run by France's state-owned energy company EDF, a union official told Reuters.

Protesters cut the power supply at the Kembs lock, located south of the city of Strasbourg near the German and Swiss borders, CGT union representative Philippe Charpentier said, adding no vessels had passed through the lock since Wednesday evening.

French unions have called on workers to walk off the job and join protest rallies on Thursday for a 12th nationwide day of protests against a bill that will raise the retirement age in France.

Some trains will be cancelled, and strike action is also expected among refinery workers, garbage collectors and teachers, at a time when opinion polls show a wide majority of voters still oppose lifting the retirement age by two years to 64.

Traffic has been blocked on the upper Rhine previously as part of the protests, heavily delaying the transit of goods on one of Europe's busiest rivers. (Reporting by Forrest Crellin; Writing by Tassilo Hummel; Editing by Kenneth Maxwell)