BERLIN (Reuters) - German public sector workers will extend strikes to airports across the country, labor union Verdi said on Monday, predicting flight disruption as it seeks to increase pressure in pay talks.

Verdi, which is asking for a 6 percent pay rise for around 2.3 million employees in various public sector roles across Germany, said ground staff and some fire services staff would be on strike on Tuesday at Frankfurt, Munich, Cologne and Bremen airports.

Frankfurt and Munich are the two biggest hubs for Lufthansa, Germany's largest airline.


Verdi said the strike at Frankfurt airport would run from 5 a.m. to 6 p.m. local time (0300-1600 GMT) on Tuesday and involve security staff, as well as workers who load and unload planes.

Frankfurt airport operator Fraport warned passengers to expect significant disruption on Tuesday. A spokeswoman said security checkpoints would likely have to be closed due to the strike.

Similar strikes four years ago led to hundreds of flight cancellations at Germany's largest airport, particularly on short haul flights.

Public transport, swimming pools, garbage collection, and childcare facilities are also areas that have been targeted by strike action in the latest pay dispute.

A third round of pay talks is scheduled for April 15 and 16.

"Employers have not yet put forward an offer. With strikes and industrial action, employees are increasing the pressure on employers to end their blocking tactics," Verdi boss Frank Bsirske said in a statement.


(Reporting by Victoria Bryan; Editing by Maria Sheahan)