Egyptians are awaiting a televised statement on the political crisis, after a deadline set by the army for a resolution to the turmoil passed.
President Mohammed Morsi has repeated his offer of a consensus government, but still refuses to step down.
Aides to Mr Morsi took to social media to describe what was happening as a military coup but there was no confirmation of this.
Armoured vehicles have been seen moving through the streets of Cairo.
There are also reports that Egyptian officials have placed an international travel ban on Mr Morsi and other senior members of the Muslim Brotherhood.
Correspondents at the main pro-Morsi demonstrations in Cairo described scuffles between the army and protesters.
In the Nasr City area of the capital, New York Times reporter Kareem Fahim tweeted that soldiers were firing into the air to disperse demonstrators.
One of Mr Morsi’s aides, Issam al-Haddad, wrote on his Facebook page that he was “fully aware” his words might be the “last lines I get to post on this page”, adding that what was happening was a “military coup”.
Defiant speech
When the deadline set by the army passed earlier on Wednesday, cheers echoed in Cairo’s Tahrir Square, where tens of thousands of protesters had gathered.
The army had earlier held meetings with political and religious leaders to discuss the crisis.
But the ruling Freedom and Justice party – the political arm of Mr Morsi’s Muslim Brotherhood – stayed away from these talks.
Mr Morsi’s opponents say he and the Muslim Brotherhood are pushing an Islamist agenda onto Egypt, and that he should stand down.
In a defiant televised speech on Tuesday evening, Mr Morsi said he would give his life to defend constitutional legitimacy, and blamed the unrest on corruption and remnants of the ousted regime of Hosni Mubarak.
Army chief Gen Abdel Fattah al-Sisi was reported to have met his top commanders on Wednesday – and a source close to the military told AFP news agency they had been discussing details of a post-Morsi roadmap.
The army’s plan reportedly includes an outline for new presidential elections, the suspension of the new constitution and the dissolution of parliament.
Members of the Tamarod (Rebel) movement, which has mobilised millions of demonstrators onto the streets to demand Mr Morsi’s resignation, were also part of the meeting.
So too were leading religious figures and opposition leader Mohammed ElBaradei. An opposition source told Reuters Mr ElBaradei would “urge the armed forces to intervene to stop the bloodshed”.
Gehad el-Haddad said the army had no right to offer such a plan.
“A roadmap is something that the constitution outlines and the president directs. It’s not the role of the military.”
He said the Brotherhood was open to any solution, but that it had to be through “representatives of the people”, and proposed speeding through parliamentary elections.
“If the protests on the street prove anything they prove the people of Egypt are ready to have their say. They can sweep the parliamentary election, impeach the president, change the constitution and set the roadmap that they want, but it has to be the right of the people.”
Military sources earlier told the BBC that under the draft plan, the president could be replaced by a council of cross-party civilians and technocrats ahead of new elections.
The president was put under further pressure by the resignation of six ministers from his government on Monday, including Foreign Minister Kamel Amr.
Elected president
Mr Morsi became Egypt’s first Islamist president on 30 June 2012, after winning an election considered free and fair following the 2011 revolution that toppled Mubarak.
But dissent has been growing, with protesters angry at the lack of change in post-revolution Egypt and accusing the Brotherhood of trying to protect its own interests.
“This is a president threatening his own people. We don’t consider him the president of Egypt,” said Mohammed Abdelaziz, a leader of Tamarod.
However, Mr Morsi and the Brotherhood still have significant public support, and both sides have drawn huge numbers to rallies in recent days.
Tens of thousands gathered in Tahrir Square in central Cairo on Wednesday – for a fourth straight day – to demand Mr Morsi step down.
There were outbreaks of violence in several parts of the capital: in the largest bout of unrest, at least 16 people were killed and about 200 wounded at Cairo University in Giza.
Eyewitness Mostafa Abdelnasser told AFP that Morsi supporters had come under attack from unidentified men carrying firearms.
At least 39 people have now died since the protests began on Sunday.
In the wake of the latest unrest, the UK Foreign Office has changed its travel advice for Egypt, recommending against all but essential travel to the country except for resorts on the Red Sea in South Sinai and in the Red Sea governorate.
The instability has also hit global oil prices, sending US light crude above $100 a barrel for the first time since September last year, amid concerns supply routes through the Suez Canal could be affected.
BBC
