The walkout by staff at Berlin's Tegel and Schönefeld airports were to last from 0500 local time (04:00 UTC) to around 1100 on Wednesday, trade union Verdi said.

Around 2,000 ground staff - including those dealing with flight check-ins and baggage handling - were to take part in the strike, it added.

Others involved in the six-hour walkout were flight marshallers and plane refueling crews.

A spokesman for Berlin's airports said he expected severe disruption.

Hamburg airport was also expected to be disrupted, and flight crew, baggage handlers, terminal bus drivers and cleaners were expected to take part, Verdi said.

Air Berlin confirmed it had canceled about 60 flights to and from Berlin on Wednesday.

Passengers were warned to expect severe delays to baggage handling for flights arriving at or leaving the two airports, and were advised to travel with just hand luggage.

Verdi said it was negotiating with the airports authority for better wages, working hours and promotion opportunities for its members.

Germany's biggest white collar union said talks with employers over raising hourly wage rates to 12 euros ($12.82) per hour from around 11 euros had stalled.

mm/jm (AP, dpa)