Jan Jambon arrives for a Minister's council meeting of the federal government in Brussels, on May 13, 2016 | Nicolas Maeterlinck/AFP via Getty Images Jan Jambon: 100 ISIL fighters in Belgium may be planning attacks Interior minister says some foreign fighters return disillusioned while others could have instructions to carry out attacks.

Around 100 returned foreign fighters from Syria may be planning terror attacks in Belgium, Interior Minister Jan Jambon said Thursday in New York.

Speaking at a press conference with U.S. counter-terrorism officials, Jambon said 300 people from Belgium have traveled to the Islamic State of Iraq and the Levant and 200 have returned, according to an NBC report.

Of those who have returned, the interior minister said half had become disillusioned with ISIL after witnessing atrocities and could be "used" to dissuade other potential recruits. However, he said the others could have returned with instructions to commit terror attacks in Europe.

Jambon said authorities were on high alert across the Continent, but "we don't have precise information about a current attack."

German police announced Thursday they had arrested three men, all Syrian nationals, thought to have been planning to launch bomb and gun attacks in Düsseldorf, in western Germany. A fourth Syrian man, linked to the plot, is in detention in France.

Members of the terror cell responsible for the March 22 bombings in Brussels, which killed 32 people, had returned from the battlefield in Syria.

“The attacks came too early,” Jambon said Thursday, according to the New York Times, explaining that efforts to improve intelligence-gathering and sharing by Belgian authorities were accelerated after March 22.

“I think we have made a lot of progress,” he said.

A report by the International Centre for Counter-terrorism in April found Belgium has the highest rate of foreign fighters per capita, and that between 55 and 130 had returned to the country.