A steep decline in Turkey's tourism revenue in the first half of the year contributed to a widening deficit in the balance of payments, figures released Thursday showed, owing to unrest in the country and a diplomatic row with Russia.

There is concern the failed coup attempt on July 15 could have further negative consequences for the sector, which is already reeling from concerns over a spate of terrorist attacks, including one in June at the Ataturk international airport in Istanbul.

In the first six months of the year, revenues from tourism were down 41 per cent, according to Turkey's central bank TCMB. Net revenues in June sank by about half compared to the same time last year.

‘Considering that July-September is the peak season for tourism, the loss in the second half of the year will likely be larger than in the first half,’ Turkey's Finansbank wrote in a research note.

The number of foreign visitors to Turkey dropped 41 per cent in June, government data showed. This followed months of steady declines, each getting progressively worse.

The number of passengers traveling through Turkish airports has declined, government data shows, while the flagship Turkish Airlines posted a loss of about 420 million dollars in the second quarter. Third quarter data for the carrier is out this month.