FRANKFURT/BERLIN (Reuters) - Tens of thousands of passengers were stranded in Berlin on Friday as a strike by ground staff led to the cancellation of nearly 700 flights operated by airlines including Air Berlin, Ryanair and Lufthansa.

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Berlin Airport, which operates Tegel and Schoenefeld airports, said almost all flights from the German capital had been grounded, with 466 flights canceled at Tegel and 204 at Schoenefeld as of 0900 GMT.

The strike by ground staff, who want an increase in their hourly pay to 12 euros ($12.71) from 11 euros, is due to run for 25 hours from 0400 local time (0300 GMT) on Friday.

Enrico Ruemker, strike leader at trade union Verdi, told Reuters TV that workers were ready to take further strike action if they did not receive a “reasonable” offer, although the union remained open to talks at any time.

The industrial action comes as many trade visitors try to make their way home from the world’s biggest tourism trade fair, the ITB, which ends in Berlin on March 12.

Some delegates left the trade fair early to avoid the strike while others told Reuters they faced long train journeys or detours to other German airports such as Hamburg or Dresden.

Air Berlin said it had canceled 202 flights, with only long-haul routes and flights to and from Dusseldorf still operating. It offered passengers vouchers for train tickets to their German destinations or flights from Hanover.

Irish budget carrier Ryanair canceled 77 flights to or from Berlin and said it was offering customers a full refund, free transfer onto the next available flight or a free transfer onto an alternative flight route.

German flagship Lufthansa said it had had to cancel 68 flights between Berlin, Frankfurt and Munich, affecting about 10,000 passengers, who could rebook or cancel for free.

“Everything should return to normal on Saturday,” a Lufthansa spokesman said.

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