Germany's main union Ver.di announced that the airports of Frankurt, Munich, Cologne-Bonn, Dusseldorf, Hamburg, Hannover and Stuttgart would be hit by the strikes.

The action at Frankfurt, Germany's largest airport, is set to last from 3.30 a.m. (0230 UTC) until 2.30 p.m. (1330 UTC) on Thursday. Staff involved in ground and freight handling, as well as maintenance, administration and security, are all expected to take part in the walkout. The airport warned passengers that they should expect "major disruptions and flight cancellations."

Away from Frankfurt, Ver.di said on Tuesday there would also be strikes at the other major airports listed, where early shifts would be taking part in the action. The walkouts were set to last no later than 2 p.m. (1300 UTC).

Lufthansa, Germany's largest airline, has said it expects significant disruption and said it would make an announcement on Wednesday about potential flight cancellations, as well as possible alternative travel arrangements.

The strikes are part of a wider disagreement, with the union asking for a pay rise of 3.5 percent - as well as a 100 euro ($138) one-off payment - for 2.1 million federal and municipal workers. Talks aimed at settling the dispute are due to resume next week.

rc/jm (AP, Reuters)