Egypt's Muslim Brotherhood called for a 'day of anger' Thursday to mark the first anniversary of the military overthrow of president Mohamed Morsi, which unleashed a violent crackdown that all but crushed the Islamists.
Police closed off several main squares in Cairo and beefed up security ahead of the anticipated protests.
Morsi's Muslim Brotherhood movement was listed as a terrorist group after his overthrow and many of its leaders, including Morsi, jailed.
The ex-army chief who toppled him, Abdel Fattah al-Sisi, has since replaced him as president.
The protests on Thursday will be seen as a test of the Islamists' strength, with the Brotherhood-led Anti Coup Alliance having issued an aggressive rallying cry on Wednesday demanding a "day of anger" to mark Morsi's ouster.
Despite the crackdown, the Islamists, joined by some allies, have insisted on continuing their protests in the hope, they say, of making the country ungovernable for Sisi.
Since Morsi's ouster on July 3 after a turbulent year in power, at least 1,400 people have been killed in street clashes, and more than 15,000 thousand have been imprisoned.
Among the Brotherhood leaders arrested was supreme guide Mohamed Badie, who was sentenced to death in a speedy mass trial.
Militants have launched scores of attacks that killed several hundred policemen and soldiers, mostly in the restive Sinai peninsula.
Rights groups say the crackdown has been the bloodiest seen in Egypt in decades.
"A surge in arbitrary arrests, detentions and harrowing incidents of torture and deaths in police custody recorded by Amnesty International provide strong evidence of the sharp deterioration in human rights in Egypt in the year since President Mohamed Morsi was ousted," the London-based Amnesty said in a statement.
The repression has further divided Egypt, a regional powerhouse and the Arab world's most populous country, with a quickly growing population of 86 million stretching its dilapidated infrastructure.
  -'Revolutionary defiance'-
The military had overthrown Morsi after days of huge protests demanding the resignation of the polarising Islamist. Almost 23 million voters went on to endorse Sisi in a May presidential election against a weak leftist candidate who garnered only several hundred thousand votes.
Sisi's supporters view him as a strong leader who can restore stability in the often tumultuous country.
Yet the Brotherhood, which had won every vote since an uprising toppled veteran strongman Hosni Mubarak in 2011, still commands a loyal following.
"Let us turn our wealth of revolutionary defiance into an overwhelming power," the Anti Coup Alliance said in its statement on Wednesday.
Police were also on alert for militant attacks, after a man was killed overnight apparently preparing an explosive in an apartment south of Cairo, security officials said.
In Cairo, a small bomb went off inside a car near a military installation late Wednesday. Police arrested a man who was in the car, while another escaped.
The incidents came after two senior police officers were killed trying to defuse bombs outside Sisi's Cairo palace on Monday.
The government says the Brotherhood has been behind the militant attacks, a charge the Islamist group denies.