We filed the appeal yesterday, Orascom Telecom spokeswoman Manal Abdel Hamid told Reuters, without giving more details.
Orascom (ORTEq.L) and France Telecom, Mobinil's main shareholders, have been locked in an ownership row over the mobile operator, Egypt's largest by subscribers, since 2007. Neither has a majority stake in Mobinil.
An appeals committee on Saturday rejected a request by Orascom that the regulator scrap an earlier decision to approve the France Telecom purchase.
France Telecom (FT) subsidiary Orange Participations offered to buy all Mobinil's outstanding shares for 245 Egyptian pounds ($44.63) each beginning on Dec. 15. The offer ends on Jan. 14.
Orascom argued that France Telecom should have offered 273 pounds for the shares, equivalent to a price set by an arbitration court in April for Mobinil shares held by Orascom through a holding company.
A telecoms analyst at brokerage EFG-Hermes told Reuters this week that if market heavyweight Orascom Telecom were to sell its shares, it could net around $1.5 billion from the deal.
Orascom sought an extra $800 million in capital from its shareholders this month to cover a potential cash shortfall pending the resolution of a separate dispute with the Algerian authorities over taxes at its Algerian unit Djezzy.
Orascom runs mobile phone operations from North Africa to North Korea, and earlier this month won approval in Canada to go ahead with a startup wireless operation called Globalive, in which it owns an indirect stake. (Writing by Shaimaa Fayed; editing by Caroline Drees/Will Waterman)