The union representing around 70,000 grocery workers in Southern California has called a strike after workers voted to reject a contract offer.

A four-year-old contract between the United Food and Commercial Workers Union and three of California's top supermarket chains, Albertsons, Kroger's Ralphs and Safeway's Vons, expired on 5 October, sparking a labour dispute based on health-care costs, reported Reuters.

Contract talks broke down on Saturday, prompting the first grocery strike in Southern California in 25 years.

All three supermarket chains have kept stores open, having hired replacement workers in preparation for a possible strike.