Five terrorism suspects have been detained after a coordinated operation in three Swedish cities, police said Tuesday. The suspects are believed to have international links to Islamist extremism, according to Sweden's domestic security agency.

Agency counterterrorism deputy head Susanna Trehorning said the case was "one of several" that they were working on "after the protests that were directed at Sweden in connection with the highly publicized burning of the Quran in January."

She said the suspects were linked to international "Islamic extremism," but that no concrete attack had been imminent.

"The Security Service often needs to act early in order to avert a threat. We can't wait until a crime has been committed before we act," the security agency said in a statement.

Trehorning told Swedish broadcaster SVT that the suspects were in "a planning phase" and that they "had not immediately thought of doing anything here and now."

Burning of Quran sparks protests 

Earlier this year, far-right Danish-Swedish politician Rasmus Paludan sparked international outrage, particularly in the Muslim world, when he publicly lit a copy of the Muslim holy book on fire in Stockholm. The incident was part of an event organized by pro-Russian journalist Chang Frick, and one of several such demonstrations Paludan has taken part in.

Protests in front of Swedish embassies for allowing the demonstration were called in several countries, including Iran and Bangladesh.

The incident also caused diplomatic headaches for Sweden's bid to join the NATO alliance, a process already made difficult by disagreements with Ankara. Turkey paused NATO negotiations with Sweden as a result of the incident, which police had authorized ahead of time. The incident had taken place near the Turkish embassy in Stockholm.

Court overturns ban on Quran-burning rallies

Also on Tuesday, Sweden's Administrative Court overturned a February police decision to ban two planned Quran-burning protests. 

Officers had argued that further demonstrations make Sweden "a higher priority target for attacks."

According to the court, security risk concerns were not enough to justify a ban on the demonstrations. It ruled that freedom of assembly and demonstration are constitutionally protected rights.

The "police authority did not have sufficient support for its decisions," Judge Eva-Lotta Hedin said in a statement.

vh/es (Reuters, AFP, AP)