FRANKFURT (AFP) — Two Afghans linked to the Islamic State group were arrested in Germany on Tuesday on suspicion of planning an attack around Sweden’s parliament in retaliation for Koran burnings, prosecutors said.

Suspects Ibrahim M.G. and Ramin N. were detained in the Gera area of eastern Germany after being charged with plotting “to use firearms to kill police officers and other people in the area of the Swedish parliament in Stockholm,” prosecutors said.

“The pair made concrete preparations for this in close consultation with officials” from a regional branch of IS, the prosecutors added.

“In particular, they researched conditions around the possible crime scene on the internet and tried several times — albeit unsuccessfully — to procure weapons.”

Swedish Prime Minister Ulf Kristersson said his country’s security services were in close contact with German authorities about the “very serious information” that had emerged.

“Sweden has faced a very threatening period,” he added.

Sweden and neighboring Denmark last year saw a spate of public desecrations of the Koran, including burnings, mainly by immigration opponents, which sparked widespread outrage in Muslim countries.

In August, Sweden’s SAPO intelligence service raised its threat level to four on a scale of five.

Two months later, two Swedish football fans were killed in a “terror attack” in Brussels, which was carried out by a Tunisian living illegally in Belgium, ahead of a Belgium-Sweden international match.