Türkiye has said no concrete threat has been identified, after a group of individuals with alleged links to the Islamic State was apprehended. Local news sources reported claims by Istanbul police that the group had "received instructions for acts targeting consulates of Sweden and the Netherlands."

The detentions come at a time of heightened security concerns in Türkiye's main tourist hub and largest city.

On Thursday, the ambassadors of nine Western nations including the United States, France and Sweden were summoned to the foreign ministry in Ankara. The diplomats were challenged over the decision to temporarily shut their country's consulates in Türkiye or issue travel warnings to citizens.

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The closures follow angry protests in the Turkish republic and elsewhere in the Muslim world after a copy of the Koran was set alight by a right-wing nationalist in Stockholm. The U.S. embassy says "possible imminent retaliatory attacks by terrorists" could take place in popular areas like the city's historic Beyoglu, Galata and Taksim neighborhoods. 

Warnings have also been issued about possible threats to non-Muslim places of worship. 

In Jerusalem, former Prime Minister Naftali Bennett urged Israelis to "show personal responsibility and safeguard their security" by avoiding travel to Türkiye. Arguing that no evidence had been presented to back up the claims, Foreign Minister Mevlut Cavusoglu denounced the move, saying "this does not fit friendship or the spirit of alliance."

Ankara later responded by cautioning Turkish citizens in the U.S.and Europe over "possible Islamophobic, xenophobic, and racist attacks." 

Türkiye's relations with the EU remain fraught as Ankara continues to block accession attempts by Sweden to join NATO, in part over the Koran-burning incident. Sweden's accession along with that of Finland is due to be finalized at the NATO summit in Vilnius this July, two months after Türkiye goes to the polls in presidential and parliamentary elections. 

The prime ministers of Finland and Sweden say they remain committed to joining NATO at the same time, after President Erdogan hinted at a change in policy towards Helsinki. Finnish Prime Minister Sanna Marin said in response that "Sweden also ticks all the boxes that are needed to become a member of NATO."