Protests in Stockholm on Saturday against Turkey and Sweden's bid to join NATO, including the burning of a copy of the Koran, sharply heightened tensions with Turkey at a time when the Nordic country needs Ankara's backing to gain entry to the military alliance.

"We condemn in the strongest possible terms the vile attack on our holy book ... Permitting this anti-Islam act, which targets Muslims and insults our sacred values, under the guise of freedom of expression is completely unacceptable," the Turkish Foreign Ministry said.

Its statement was issued after an anti-immigrant politician from the far-right fringe burned a copy of the Koran near the Turkish Embassy. The Turkish ministry urged Sweden to take necessary actions against the perpetrators and invited all countries to take concrete steps against Islamophobia.

A separate protest took place in the city supporting Kurds and against Sweden's bid to join NATO. A group of pro-Turkish demonstrators also held a rally outside the embassy. All three events had police permits.

The Koran-burning was carried out by Rasmus Paludan, leader of Danish far-right political party Hard Line. Paludan, who also has Swedish citizenship, has held a number of demonstrations in the past where he has burned the Koran.

Sweden and Finland applied last year to join NATO following Russia's invasion of Ukraine but all 30 member states must approve their bids. Turkey has said Sweden in particular must first take a clearer stance against what it sees as terrorists, mainly Kurdish militants and a group it blames for a 2016 coup attempt.

Finland and Sweden signed a three-way agreement with Turkey in 2022 aimed at overcoming Ankara's objections to their membership of NATO. Sweden says it has fulfilled its part of the memorandum but Turkey is demanding more, including extradition of 130 people it deems to be terrorists.

(With input from Reuters)