"We do not recognize the interim president," "7Elsob (7morning) movement said on its official Facebook page.
An Alexandria court has jailed 14 girls to 11 years in prison for "illegal assembly and joining a banned group."
The group described as presidential pardon for the girls as an attempt to win interim authorities a "lost legitimacy".
Presidential adviser Sakina Fouad said Friday that the interim president has "pledged to take action" over the girls' issue.
Fouad appealed to Muslim Brotherhood members "not to undermine the homeland".
Egypt has remained in a state of turmoil since the July 3 ouster of elected president Mohamed Morsi following mass protests against his presidency.
The unconstitutional change of government is described by Morsi's supporters as a military coup, while opponents hail it as a military-backed "popular uprising."
Supporters of the ousted president have been staging rallies on almost a daily basis to denounce what they describe as a "military coup" and demand his reinstatement.