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BERLIN/FRANKFURT (Reuters) - Trade union Verdi has called on airport security staff at eight German airports to go on strike on Tuesday, including the nation’s largest hubs Frankfurt and Munich, ramping up pressure in its push for higher pay.

Smaller regional airports affected by the all-day strikes include Hanover, Bremen and Hamburg, Verdi said on Monday.

German airport association ADV said in a statement that about 220,000 passengers are likely to be affected by cancellations and delays.

The walkouts follow strikes at five airports last week and were denounced by ADV as excessive.

More than 640 flights in Germany were canceled on Jan. 10 because of strikes by security staff at Duesseldorf, Cologne and Stuttgart airports. Two Berlin airports were affected earlier that week.

Fraport, operator of Frankfurt airport, Germany’s busiest hub, said it expects severe disruption on Tuesday.

Verdi is calling on 350 employees at Munich airport to stop working from 0230 GMT until 1900 GMT, a union representative told Bavarian radio on Sunday.

Munich airport said that its passenger security checks are carried out by a public-sector contractor whose workers would not go on strike. However, it added that some flights to and from airports affected by the walkout would be canceled.

Verdi is in wage negotiations on behalf of 23,000 security workers in Germany. Talks with employers are due to resume on Jan. 23.