Travel firm Thomas Cook said cancellations of holidays to Tunisia after a beach resort gun attack, along with concerns regarding Greece's potential exit from the euro, were expected to impact 2015 profit by about 25 million pounds ($39 million).

However, the group said on Thursday that overall it continued to expect growth in full-year earnings on a constant currency basis.

Shares in Thomas Cook have fallen 13 percent since June 26 when a gunman killed 38 foreign holidaymakers in a Tunisian beach massacre claimed by Islamic State militants.

Thousands of tourists rushed to leave the country after Britain warned another attack was highly likely. Thomas Cook subsequently canceled all trips to the North African country until October.

Thomas Cook said it swung to an operating profit for the three months ended June 30, its fiscal third quarter, of 3 million pounds from a 50 million loss a year before, a 12th consecutive quarter of improved profitability, on revenue up 0.2 percent to 1.95 billion.

It said summer 2015 holidays were 78 percent sold, the same as this time last year, while customer bookings had generally improved in most markets over the last few weeks.

The firm noted the foreign exchange translation impact on 2015 profit was expected to be 39 million pounds, up from 25 million previously indicated, following further depreciation of the euro and Swedish krona against sterling.