From the BBC:
Egypt's supreme court has caused widespread alarm by calling for the dissolution of the lower house of parliament and for fresh elections.
Two days before Egyptians choose a new president, it has declared last year's parliamentary vote unconstitutional.
Muslim Brotherhood presidential candidate Mohamed Mursi said the decision "must be respected".
But other political figures have expressed anger amid fears that the military wants to increase its power.
Another senior Muslim Brotherhood politician, Essam Al-Arian, said the ruling on parliament would send Egypt into a "dark tunnel".
The Brotherhood's Freedom and Justice party won 46% of the vote in the three-month parliamentary poll and Mr Arian warned that the decision would leave the incoming president without a parliament or a constitution.
Islamist Abdul Moneim Aboul Fotouh, who took part in the first round of the presidential vote in May, said that dissolving parliament amounted to "a total coup, anyone who imagines that the millions of youths will let this pass is dreaming."
Protesters gathered in Tahrir square in the centre of Cairo after the ruling.
The Salafist Al-Nour party, which has the second biggest representation in parliament, said the ruling showed "a complete disregard for the free will of voters".
Parliament speaker Saad El Katatny was equally scathing, arguing that no-one had the authority to dissolve parliament.
In a separate ruling, the supreme court also decided that former Prime Minister Ahmed Shafiq could continue to run for president in the June 16-17 presidential run-off election, rejecting as unconstitutional a law that would have barred him from standing.
Under the Political Exclusion Law, passed by parliament, senior officials from former President Hosni Mubarak's regime were banned from standing for office.
Mr Shafiq is standing against Mr Mursi in a tight run-off. He told supporters that the court had made a "historic ruling and verdict that meant there was no way for anyone to do particular laws for particular people."
Egypt's ruling military council (Scaf) held an emergency meeting after the two court rulings and later confirmed that the election would go ahead as planned, and urged Egyptians to vote