The BBC's Jon Leyne in Cairo said the announcement caught everyone by surprise, and all over the city drivers honked their horns and people fired guns into the air.

But the army takeover looks very much like a military coup, our correspondent adds.

The constitution has been breached, he says, because officially it should be the speaker of parliament who takes over, not the army leadership.

Hope for the best, plan for the worst. So far the Egyptian military have been on the right side of this situation but we have no guarantees what happens next. This is the end of the beginning, not the end.