"The Tehran prosecutor's spokesman said Van den Bosch, Vincent Binfleur and Diego Gomatio (all names as transliterated from Persian) were arrested two months ago and were freed by order of Tehran prosecutor Abbas Jafari Doulatabadi.

"They were handed over to the Belgian ambassador in Tehran," the report added without elaborating.

It was the first word on the trio's arrest and the Belgian foreign ministry denied all comment.

"We are not making any comment, we're neither confirming it nor denying it," ministry spokesman Bart Ouvry said in Brussels.

Asked if there would be further word later, he said: "Certainly not tonight."

The Belgian embassy in Tehran too refused to comment.