The Netherlands is investigating media reports that a sleeper cell of the Isis jihadist group has been hiding among people living at a Dutch refugee camp, officials said Tuesday.
"We have heard these reports and an inquiry is being undertaken into this," Justice Minister Ard van der Steur told MPs during a parliamentary session.
He refused to go into any detail, saying only that "in this kind of case information is internationally shared at every level."
The French newspaper Le Monde reported on Tuesday that a Syrian suspect who turned himself into French police had revealed the existence of the sleeper cell, split between a camp in the eastern Dutch town of Nijmegen, close to the German border, and the German city of Düsseldorf.
The suspect, identified as Saleh A, said there were about 20 people in the cell of which he and another man Hamza C. were the heads, Le Monde said.
Contacted by AFP, the Dutch prosecution service refused to make any comment about the report.
German federal prosecutors announced last week that three Syrian men had been arrested in Germany over an alleged plan to launch a suicide attack there for Isis.
According to the suspects' plan, two attackers were to detonate suicide vests while the others were to kill passersby with guns and explosives in Düsseldorf, prosecutors said in a statement.
Saleh A. and Hamza C. had joined Isis in early 2014 in Syria, where "they were ordered by the group's leadership to carry out an attack in the old town of Düsseldorf," the German prosecutors said.
Since the November attacks in Paris and the March suicide bombings targeting the Brussels airport and metro, Dutch officials have repeatedly sought to reassure people that they are being vigilant about security.
The Netherlands took in a record 58,800 migrants last year, almost double the number which arrived in 2014 as Europe grapples with its worse refugee crisis since the Second World War.
Some 3,000 have been housed in Nijmegen, the biggest camp in the country erected to house asylum seekers.