An Egyptian court has ruled that the nation's Islamist-dominated legislature and constitutional panel were illegally elected.
The court said the law governing the elections of the Islamist-dominated council was unconstitutional, as were the rules for the selection of the members of a committee that drafted the constitution.
The ruling said the upper house, or Shura Council, would be dissolved once the new parliament is elected.
A date has yet to be set for the elections.
The Supreme Constitutional Court (SCC) building in southern Cairo was surrounded earlier on Sunday by police ahead of the crucial ruling, which could see tensions resurface between supporters of Mursi and his opponents.
Fifteen police riot trucks were stationed near the building, AFP reporters said.
The case against the Shura Council is based on several challenges by lawyers of the law that governed the election of its members.
Mursi originally called elections for April but postponed them when the court annulled the decree setting the dates. The president said elections could begin in October, completing the democratic transition from Mubarak’s rule.
Both the upper and lower houses were elected under the same electoral law, which the SCC last year deemed invalid, prompting the dissolution of parliament.
Legal opinion is divided on what could happen should the Shura Council be dissolved, and whether laws and texts it has issued would be annulled.