London - At the end of July, the beaches of southern Turkey and the bars of Istanbul should be busy with foreign visitors, as the tourism season peaks.

But instead the turmoil in the nation means its tourist industry is experiencing the worst summer since the early 1990s.

Terrorism and political instability has triggered an unprecedented switch away from Turkey. Figures just released for June - before the attempted military coup - show a fall of 41 percent in international arrivals compared with 2015. The travel industry expects the numbers to get significantly worse for the height of the season.

The trend in the statistics issued by the Ministry of Culture and Tourism is for the decline to increase by a further six percent monthly. This points to a fall of 47 percent in July and 53 percent in August.

However, the outcome could be even worse if many prospective tourists are deterred by the attempted coup on 14-15 July and the government crackdown since then. A state of emergency was declared on 21 July and is expected to prevail for three months, coinciding with the end of the tourist season.

The market leader from the UK and Germany to Turkey is Thomas Cook. It revealed that it had cut capacity to Turkey by 40 percent, leading to a £100m reduction in revenue between April and June this year.

Peter Fankhauser, the chief executive, blamed the terrorist attacks earlier the year for a drop in demand.

The June figure for UK visitors to Turkey shows a fall of slightly more than one-third. In 2015, British holidaymakers arrived at a rate of 12 000 a day; this year, the number is below 8 000.

The Foreign Office warns British travellers that the security environment “remains potentially volatile” and is urging them to carry passports and printed copies of e-visas at all times.

One hope for the Turkish tourism industry is that the slump in sterling since the EU referendum could trigger more demand from British visitors. Costs are far lower than in Spain - which is gaining millions more holidaymakers this year as a result of the downturn in travel to Turkey.

Terrorist attacks in Brussels and Turkey cost the Thomas Cook Group £100m in lost revenue between April and June this year. The firm's third-quarter results show bookings down five percent compared with 2015. The drop is due to a sharp cut in capacity to Turkey; elsewhere, bookings rose eight percent as planes were moved to serve Spain, Portugal and long-haul destinations.