A billboard displayed this week in Istanbul's main airport warned travellers against visiting Sweden, describing it as having the highest rate of rape in the world, the latest salvo between EU-candidate Turkey and its European allies.

Ties between Ankara and Europe have worsened since last month's failed coup, with Turkey accusing its Western allies of insensitivity, saying they were more concerned about a subsequent crackdown than the coup itself.

"Travel warning! Do you know that Sweden has the highest rape rate worldwide?" read the large advert, which was put on display on Thursday next to a moving walkway in the departures section of Ataturk Airport's international terminal.

Travellers at the airport glanced at the billboard as they passed along the moving walkway, Reuters TV footage showed.

Alongside the message was an image of the front page of the pro-government Gunes newspaper that read: "Rape country Sweden".

State-run Anadolu Agency said a private company had paid for the advertisement.

Turkey's Foreign Minister Mevlut Cavusoglu told reporters on Monday that Turkey had summoned Sweden's ambassador to protest comments from Foreign Minister Margot Wallstrom regarding Turkish legislation on sexual abuse of children.

"(The) Turkish decision to allow sex with children under 15 must be reversed. Children need more protection, not less, against violence, sex abuse," Wallstrom had written on Twitter.

Cavusoglu said her comments were a scandal and based on false rumours, dismissing them as "the result of racism and anti-Islam sentiment in Europe".

Her comments were in reference to a decision by Turkey's constitutional court annulling a penal code provision punishing all sexual acts involving children under the age of 15 as "sexual abuse" and asking parliament to draw up new legislation.

On Sunday, Turkey summoned Austria's charge d'affaires to protest over a headline on an electronic news ticker at the airport in Vienna that allegedly read, "Turkey allows sex with children under the age of 15". Austrian officials played down the matter as one of freedom of the press.

Austrian Chancellor Christian Kern has said the EU should end accession talks with Turkey, prompting Cavusoglu to refer to Austria as the "capital of radical racism".