"TUI is cancelling all trips to Egypt up until and including September 15 in response to the foreign ministry's latest assessment of the situation there," the group said in a statement.
Thomas Cook announced a similar decision, also until September 15.
"Given the current situation in Egypt and the security upgrade by the foreign ministry, Thomas Cook's German tour operators -- Neckermann Reisen, Thomas Cook, Bucher Last Minute and Oger Tours -- will not be bringing any new holidaymakers to Egypt and cancel any trips that have already been booked," the company said in a statement.
In particular, tourists were being urgently told to avoid travelling to Cairo and the main tourist centres in Upper Egypt such as Luxor, Assuan and the Nile Delta, the ministry said.
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Tourists already in those areas are being urged to take very special care during their visit and to heed the advice of hotels and tour operators, the ministry added.
Holidaymakers in the Red Sea could remain there, since the situation in those regions was still calm.
Should any Thomas Cook or TUI customers wish to return home early they should contact their tour managers, the companies said.