Swedish-Danish politician Rasmus Paludan on Saturday torched the Islamic holy book in front of Ankara's embassy in Stockholm just as Turkey holds up Sweden's application to enter the transatlantic alliance.

"Burning books that are holy to many is a deeply disrespectful act," State Department spokesman Ned Price told reporters.

"It's repugnant," he said, also calling the incident "disgusting" and "vile."

Price said the burning was the work of "a provocateur" who "may have deliberately sought to put distance between two close partners of ours -- Turkey and Sweden."

He "may have deliberately sought to have an impact on the ongoing discussion regarding the accession of Sweden and Finland to NATO," Price said.

Price defended the stance of Sweden, saying that it upholds "freedom of association" and that an act "can be lawful and awful at the same time."

Turkish President Recep Tayyip Erdogan, who has Islamist political roots, voiced fury over the incident including Sweden's permission for the rally to take place.

Erdogan said that Sweden should not expect support on joining NATO, after he earlier demanded that Stockholm take action on Kurdish militants which Turkey considers terrorists.

Sweden and Finland last year applied to enter the Western alliance, shedding earlier reluctance to annoy Russia after their giant neighbor invaded Ukraine, which had unsuccessfully sought to enter NATO.

Under the rules of the alliance, all members must approve new members. Only Turkey and Hungary have not given their green light, with Hungarian Prime Minister Viktor Orban promising that parliament will do so next month.