About 150 workers providing services to oil and gas companies operating in the UK North Sea have agreed to start strike action on April 5, according to the Unite union.

The action will affect production platforms operated by Shell Plc and Harbour Energy Plc, the union said in an emailed statement.

Walkouts were announced two weeks ago, though no start date was given at that point. This is the “opening round” in industrial action that could shut down dozens of platforms, Unite said.

The workers set to go on strike are employed by Sparrows Offshore Services. A series of stoppages will continue until June 9, according to the statement.