Europe's largest tour operator said sales for this summer were up 4% compared to 2012, while bookings in January were up 2%.
A 9% hike in summer bookings in the UK, and a 10% increase in Nordic countries helped counteract falling demand in France and Germany as the eurozone's debt crisis continues.
The company said around a third of its mainstream summer holidays had been sold so far, and that it expected full-year profit to be at the top end of expectations.
But despite the strong bookings, the British company reported a 12% increase in its loss before tax to £178m in the last three months of 2012.
The company's chief executive Peter Long said: "Our leading position in the UK has further benefited from increased market share as a result of higher demand for our unique holidays.
"Across all our key markets demand for the overseas holiday remains strong, despite the overall economic environment.
"We are confident that our customer focused strategy is driving performance and based on current trading we expect to be towards the top end of our roadmap guidance of 7-10% underlying operating profit growth for the 2013 financial year."
The world's oldest travel group, which has been struggling since the start of the downturn, also reported improving sales in the UK.
It said its pre-tax loss in the three months to the end of 2012 was £151.7m - more than 15% down on the loss reported in the same period in the year before.
Over the last two years, Thomas Cook has issued a string of profit warnings and been forced to renegotiate its bank loans.
But the company's fortunes have been improving since its new chief executive took over in May.
Industry outsider Harriet Green oversaw a string of disposals to slash its debt, including the sale of its Indian business and several Spanish hotels.
Winter and summer bookings were in-line with expectations, the 172-year-old company said.
Ms Green added: "We have seen stronger operating performances in our major markets - the UK, Germany and the Nordics.
"I am particularly pleased with the improved performance in the UK as the benefits of the turnaround plan are reflected in its operating results.
"We have further strengthened our leadership team and the pace at which we are driving change gives me confidence that together we will achieve our near term objectives and much more."
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