At least 50 people are reportedly dead as parts of Egypt descend into further violence.
State media said a police officer died following an armed attack on a checkpoint in the capital Cairo, where the army has been deployed to guard “important and vital facilities” – and is authorised to use live ammunition.
Witnesses reported seeing the bodies of at least 20 people in rows in a mosque in the centre of the city.
Automatic gunfire echoed across Cairo and black smoke billowed from the capital’s huge Ramses Square, with a military helicopter hovering overhead looking down on the chaos.
Footage being broadcast on state TV in the country purported to show armed protesters shooting at security forces in Cairo, where tens of thousands have taken to the streets.
Sky’s Foreign Affairs Editor Tim Marshall said: “State TV’s narrative is that this is terrorism, that the (pro-Morsi) Muslim Brotherhood is behind it and that the armed forces are on the right side and are protecting people against what they call terrorism.
“There are few other sources of visual information so far.”
Tear gas could be seen during flashpoints in parts of the city, with protesters apparently hurling bottles and rocks at security forces.
AFP said four protesters were killed during battles with security forces in the Suez Canal city of Ismailiya.
Reuters said the casualties included four people in central Cairo, five in Fayoum and quoted medical sources as saying eight were killed in Damietta – around 120 miles from the capital.
It comes after hundreds were killed on Wednesday in a crackdown by security forces on supporters of ousted president Mohamed Morsi.
Thousands of pro-Morsi supporters have been marching from north-east Cairo towards the city’s centre, chanting “down with military rule”.
Barbed wire, armoured personnel carriers and armed soldiers were seen blocking an entrance to Tahrir Square, next to the Egyptian Museum, as well as side streets in downtown Cairo.
Islamist group the Muslim Brotherhood, who back the deposed leader, had earlier issued calls for a nationwide “day of rage” by millions of supporters following Wednesday’s deadly clashes.
“Despite the pain and sorrow over the loss of our martyrs, the latest coup makers’ crime has increased our determination to end them,” it said in a statement.
In a counter move, the National Salvation Front – a loose liberal and leftist coalition – called on Egyptians to take to the streets today against what it said was “obvious terrorism actions” conducted by the Brotherhood.