European travel group TUI said summer trading was very good with bookings for Greece, Turkey and Cyprus all growing strongly.

TUI also said that it was on track to increase profits by at least 10% at constant currencies this year. 

The company narrowed its underlying core loss by more than half in the first quarter to €25.4m.  

Its hotels and cruises businesses helped to boost earnings in what is typically a loss-making quarter for holiday companies, even as it took a hit from the insolvency of Austrian airline Niki. 

"Q1 2018 has shown that TUI is on track, we continue to grow," CEO Fritz Joussen said in a statement. 

Rival Thomas Cook last week said that recovering demand for trips to Turkey would help offset the impact on its business of rising costs in Spain. 

The return of Turkey is a boost for tour operators because they can earn higher margins on holidays there, whereas Spain has seen rising hotel costs and increased competition, thus hurting profitability. 

However, TUI added that demand for the Caribbean remains subdued after hurricanes swept the region, affecting its bookings from France. 

TUI was last year hit by the insolvency of Air Berlin, taking a €15m charge after having to renegotiate lease agreements that it had with Germany's second-biggest airline. 

It took another €20m write-down in the first quarter, this time linked to a wet lease contract with Niki, a former unit of Air Berlin which filed for insolvency in December. 

TUI's German airline has had to take back some planes and crew that it previously leased to Air Berlin and Niki. 

The impact on its cost base could not be fully recovered in the first quarter, but it said this should improve.