Egypt's foreign ministry said Sunday that the denunciation by the banned Muslim Brotherhood group of the recent execution of Islamist militant Adel Habara reflects the organisation's "support for terrorism."
Habara, 40, was sentenced to death in 2014 for murdering 25 army personnel in Sinai in August 2013.
Authorities executed him on Thursday days after a top court rejected his final appeal.
A day later, the Brotherhood -- designated by the government as a terrorist group in late 2013 — condemned his execution as a "new crime [by the regime] of violating human rights and abusing the justice system."
The Brotherhood had said in a statement that Habara was not granted a fair trial and that authorities failed to offer him the internationally recognised human and legal rights he needed to defend himself.
The foreign ministry's statement said that "the [Brotherhood's] statement sympathises with a militant who carried out a terrorist attack that was condemned by the entire international community," referring to the 2013 Sinai attack.
"This is a categorical response to those who still doubt that the Brotherhood is a terrorist organisation," the statement added.
The ministry said that the once-ruling group failed to acknowledge the rights the court had granted Habara, including multiple appeals other judicial and legal proceedings the trial went through over the course of three years.
Egyptian authorities are battling an Islamist insurgency based in the border North Sinai region.
President Abdel-Fattah El-Sisi has made crushing the militancy a top priority in his administration.