Ground staff at Berlin’s two airports will start a 25-hour strike on Monday, the Verdi unio said on Sunday, stepping up action in a pay dispute that has already caused the cancellation of around 1,000 flights.

Workers at Berlin’s Tegel and Schoenefeld airports will walk out at 4am local time (0300 GMT) on Monday and end the action on Tuesday morning at about 5am local time (0400 GMT), said Verdi in a statement.

Lufthansa said it would cancel all flights on Monday from Frankfurt and Munich to Berlin, and from Germany’s capital to those cities. It did not say how many flights that involved.

The unio wants an increase in pay for ground staff to €12 (Dh47) an hour from about €11 as part of a one-year collective agreement. The employer is offering about 10 euro cents more an hour over four years.

As well as Lufthansa, carriers including airberlin, easyJet and Ryanair serve the two airports.

Ground staff jobs include checking in passengers, loading and unloading planes and directing aircraft on the tarmac.

Tens of thousands of passengers were stranded in Berlin on Friday as the last strike by ground staff led to the cancellation of nearly 700 flights.