Supporters of the deposed President Mohamed Morsi continued to rally after an apparent call by Egypt's army chief to crack down on dissenters.

Military helicopters circled above Cairo early on Thursday morning following a "state of alert" declaration by the army.

One photo posted on social media showed a helicopter above a pro-Morsi rally in Giza.

The state of alert was declared on Wednesday after general Abdel Fattah El Sisi called for all Egyptians to rally against what he termed "violence and potential terrorism" on Friday.

In a speech to army graduates, he also denied accusations that he had betrayed the deposed president, Mohamed Morsi.

"I ask ... that next [upcoming] Friday all honest and trustworthy Egyptians must come out," Sisi said in remarks broadcast live by state media. "Why come out? They come out to give me the mandate and order that I confront violence and potential terrorism."

Despite Sisi's statement, tens of thousands of pro-Morsi protesters filled Nasr City on Thursday to demand the deposed president's reinstatement, continuing a vigil which began on July 3 when he was removed by the army.

Elsewhere in Sisi's speech, he vowed to stick to a political roadmap that laid the way for a reform of the constitution and new elections within some six months.

He said his appeal for protests was not a call for violence and expressed support for efforts for national reconciliation.

The military reacted soon after, declaring the "state of alert".

Ahmed Al-Meslemani, media adviser to the interim president Adly Mansour, later echoed the call, asking people to take to the streets to protect the "revolutionary legitimacy" and support efforts to "fight terrorism".

The Muslim Brotherhood also reacted quickly, with senior member Essam al-Erian issuing a statement directed at Sisi saying: "Your threat will not prevent millions to rally against [the] coup ... You have been always in your office conspiring."

Egypt's opposition Islamist coalition said Sisi should be tried by for crimes against humanity for calling for Friday's rally, which they said was "an announcement of civil war".

"Sisi's threats are an announcement of civil war," said the Muslim Brotherhood-led coalition at a press conference.

'State of alert'

The state of alert will include the army deploying additional troops to streets in provinces in greater Cairo and surrounding areas.

The army chief's speech came ahead of "national reconciliation" sessions called for by the interim leader Adly Mansour, and followed renewed violence in and outside the capital, in which at least three people died.

Both the Muslim Brotherhood and Al-Nour, Egypt's most powerful Salafi party, rejected invites to Mansour's first reconciliation sessions.

"For the Muslim, Brotherhood, the legitimate president of Egypt is Mohamed Morsi," said Al Jazeera's Nadim Baba, reporting from Cairo.

Since Morsi's removal, over 100 people have been killed in violence, mostly during protests.

PHOTO CAPTION

Egyptian supporters of deposed president Mohamed Morsi hold up his portrait and shout slogans, as they continue to hold a sit in outside Cairo's Rabaa al-Adawiya mosque on July 24, 2013.

Aljazeera