Saturday's statement by Hizbullah accused Terje Roed-Larsen of supporting Israel and said his position provided cover for Israeli "criminal practices."
Roed-Larsen is the UN Chief's envoy dealing with implementation of a 2004 Security Council resolution that includes demands for Hizbullah's disarmament.
Larsen on Thursday criticized Hizbullah's admission that it supported fighters in Gaza from Egypt and said there is growing concern the group has engaged in militant activities beyond Lebanon.
Roed-Larsen said that in recent weeks, "There has been a growing concern that Hizbullah has engaged in clandestine and illegal militant activities beyond Lebanese territory." He cited Egypt's announcement on April 8 that it had uncovered a plot by 49 men linked to Hizbullah to destabilize the country by carrying out "hostile operations" on Egyptian institutions and Israeli tourists.
UN Secretary-General Ban Ki-moon was alarmed by Hizbullah's admission that it was indeed helping the Palestinians via its actions in Egypt, Larsen said.