GENEVA (Reuters) - A wide-ranging decree issued by Egyptian President Mohamed Mursi raises very serious human rights concerns, U.N. Human Rights Commissioner Navi Pillay's spokesman said on Friday.

"We are very concerned about the possible huge ramifications of this declaration on human rights and the rule of law in Egypt," Rupert Colville told a news briefing at the United Nations in Geneva. "We also fear this could lead to a very volatile situation over the next few days, starting today in fact."

(Reporting by Tom Miles; Editing by Angus MacSwan)