Turkey called on NATO hopeful Sweden on Tuesday to prosecute those responsible for projecting the flag of an outlawed group onto the parliament building in Stockholm, on the day of Turkish elections that extended President Tayyip Erdogan's rule.
A Swedish parliament spokesperson said a number of people projected messages onto the building in Sweden's capital late on Sunday, adding it had no documentation about what was projected.
The warning could raise the stakes ahead of a mid-July NATO summit at which some alliance members are urging Turkey to back Sweden's membership bid, after a year of delays over concerns that Stockholm must do more to take on militant groups.
Footage first shared on Twitter by the so-called Swedish Solidarity Committee for Rojava - a reference to Kurdish regions of Syria - projected a flag of the Kurdistan Workers' Party (PKK) on the parliament building.
Another image shared by the account includes text reading "Freedom for Ocalan," referring to the PKK's jailed leader Abdullah Ocalan, which was also projected onto the building.
"We expect the Swedish authorities to investigate this incident, hold accountable those responsible, and stop self-identified members of PKK — which the EU recognises as a terrorist entity — from operating on Swedish soil," Fahrettin Altun, the Turkish presidency's communications director, said on Twitter.
The parliament spokesperson said: "During the night towards Monday, a number of people stood on a quay on the other side of the water seen from the Riksdag (Swedish parliament) building and projected messages onto the Riksdag building."
"The persons left when the Riksdag's security guards arrived," the spokesperson added in an email.
The incident took place after Erdogan won a mandate in runoff elections to carry on his muscular foreign policy in which Turkey objected to both Sweden's and Finland's bids to join NATO last year in the face of Russia's invasion of Ukraine.
Turkey ratified Finland's bid in March but still objects to Sweden, saying Stockholm harbours members of militant groups it considers to be terrorists and has not fulfilled its part of last year's deal meant to assuage Ankara's security concerns.
Bids for membership must be approved by all NATO members.
Altun said he hoped Sweden would properly enforce a new anti-terror law taking effect on 1 June, and prevent PKK members from demonstrating at a protest against Sweden's NATO membership called by the solidarity committee for June 4.
Ahmet Berat Conkar, former chair of parliament's Foreign Affairs Committee and head of Turkey's delegation at the NATO Parliamentary Assembly, said that Turkey expects more engagement from Sweden on how their terrorism laws are being implemented.
"These factors will be important in our parliament's decision on Swedish membership. But on a positive note, as you see in Finland's case, Turkey is open to NATO enlargement and we will apply the same standard to Sweden as well," he said in an interview.
