Ten teenagers suspected of planning terrorist attacks on Christmas markets were arrested in Belgium. Speaking for the Belgium prosecutor’s office, spokesman Eric Van Der Sijpt said the group had received instructions online as to how to make bombs and kill people.

“[The teenagers] were recruited by terrorist groups to prepare or commit terrorist acts,” the spokesman said.

The arrest follows the detention of a 12-year-old boy who tried to detonate a nail bomb at a Christmas market in Germany. He was described as being “strongly radicalized” and “incited and instructed" by an "unidentified member of ISIS,” according to investigators that spoke to the German Magazine Focus.

The boy reportedly planned to travel to Iraq and join ISIS last summer. He was not arrested because he is younger than the criminal age of responsibility in Germany. He was taken into foster care, however.

Citing “credible information,” the U.S. State Department issued a warning to its citizens about the “heightened risk” of terrorist attacks during the holiday season in Europe.

Alsumaria News quoted a source in Mosul who said “ISIS media outlets started to promote footage of one of the leader’s speech, at a mosque in the city of Mosul, threatening to attack European countries during Christmas celebrations.”

The group will be desperate to remain relevant after suffering a number of recent defeats in Iraq and Syria.