Egypt's interim President Adly Mansour has pledged a "battle for security to the end" against those he says want to drive the country into chaos.
In a televised speech late Thursday, Mansour said Egypt is at a "decisive moment" and must be protected against those who are looking to bring "violence and bloodshed."
"I reaffirm to you all my commitment and the government's commitment to restore security and stability in our country," Mansour said. "We will not be scared or alarmed, and we will not go easy on those who kill the innocent. We will fight a battle of security to the end, we will protect the revolution, we will build the nation and we will move forward without hesitation."
The speech came ahead of mass protests planned Friday by supporters of ousted Islamist President Mohamed Morsi, who remains in secret military detention over two weeks after his removal. Anti-Morsi activists have also called for protests.
The army on Thursday warned the protesters to remain peaceful. A spokesman said those whoever resorts to violence will "endanger his life and will be treated with utmost decisiveness, within legal bounds."
Morsi's Muslim Brotherhood does not recognize Mansour as president. It has refused to participate in a transition government or compete in upcoming elections to decide a new constitution, president and parliament.
Instead, the Islamist group hopes to keep up the pressure with constant sit-ins and protests against what it considers a military coup against Morsi, the country's first freely elected leader.
Although most of the protests have remained peaceful, dozens of people have died during clashes between groups of protesters and with police.
Earlier this month, more than 50 pro-Morsi protesters and three security officers died during an incident outside a compound where the ousted president was believed to be held.
Human Rights Watch has told VOA that the general sense of lawlessness across Egypt has led to a sharp increase in sectarian attacks and human rights abuses across the country.