Egypt's vice-presiden has resigned after 149 people were killed by police in Cairo.
Supporters of the ousted president Mohamed Morsi - who was removed from power in last month's coup - were attacked in two camps.
Police used tear gas to drive out protestors, before opening fire on the demonstrators as they ran for safety.
Government sources say 149 people have died, and 1,403 people have been injured,
Sky News says one of its veteran TV cameramen, Mick Deane, was shot and killed while covering the violence in Cairo.
Violence has also broken out in the second biggest city, Alexandria, as news of the events in Cairo filtered through.
There, pro-Morsi protestors are rioting and damaging cars and shops.
A state of emergency has been declared for the next month, and curfews are being imposed in Cairo and ten provences - including the cities of Alexandria and Suez - for this evening.
