MONTREAL -- Longshoremen at the Port of Montreal launched a four-day strike Monday morning.

The union representing striking workers gave 72-hours notice Friday to the Maritime Employers Association.

Union members affiliated with the Canadian Union of Public Employees will not provide any mooring services during the strike, except for supplies to Newfoundland and Labrador and for grain vessels in order to comply with a decision rendered by the Canada Industrial Relations Board.

The union says the dispute centres mainly on working hours.

The port says the strike doesn't affect liquid bulk handling, the Oceanex service and the grain terminal.

The Montreal Port Authority says port activities are essential to keep the economy running smoothly and, in some cases, to ensure public health and safety.

A spokesperson for the Maritime Employers Association issued a statement Monday, saying it is "surprised and extremely disappointed by the ruling of the longshoremen’s union’s executive committee to use pressure tactics such as a strike."

The association said it believes negotiating is the best course of action.

This report by The Canadian Press was first published July 27, 2020. With files from CTV Montreal.