"He was ready to restart something in Brussels," Reynders was quoted in a statement as saying at a conference in the Belgian capital. "And it may be the reality because we have found a lot of weapons, heavy weapons, in the first investigations and we have found a new network around him in Brussels."
More than 30 people have been identified as being involved in the Paris attacks in some way "but we are sure there are others", he said.
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Abdeslam, 26, is the only suvivor of the 10-man commando that carried out the 13 November Paris attacks killing 130 people and is being held at a maximum security prison in the Belgian city of Bruges.
His lawyer, Sven Mary, has said he will fight attempts to extradite his client to France and that he would file a legal complaint against a French prosecutor who divulged details to the press of his first interrogation on Saturday.
Two more suspects are being sought in connection with the killings - Mohamed Abrini, who became friends with Abdeslam when they were teenagers, and another fugitive known only by a name used on false papers, Soufiane Kayal.