Egyptian President Abdel-Fattah El-Sisi has vowed to amend laws in Egypt within days to achieve "rapid justice" against militants a day after the assassination of the country's top public prosecutor.

"Swift justice is chained to laws," El-Sisi said in televised remarks to reporters as he left a military funeral for Hisham Barakat, whose convoy was struck by a car bomb attack on Monday.

The president said criminal laws will be adjusted "within days" to "confront the developments we are facing."

"We will make amendments to laws so we can achieve justice in the swiftest possible time," El-Sisi said.

In the absence of parliament, President El-Sisi has wielded legislative authority.

The assasination of 65-year-old Barakat is the first of a high-ranking state official since the July 2013 ouster of Islamist president Mohamed Morsi.

The killing of Barakat could signal a new escalation in an Islamist insurgency unleashed by Morsi's removal.

Morsi, who hails from the Muslim Brotherhood, was sentenced to death earlier this month over incitement of murder charges in a mass jailbreak case in 2011.

However, the president said that up until now "not a single exceptional measure has been taken" in reference to the government's use of its current laws in its fight against terrorism.

El-Sisi said the judiciary would not wait for years to prosecute militants, adding that they give orders for their deadly attacks "from inside their [prison] cages."

"If a death sentence or a life term is handed down, it will be implemented."

Verdicts meted out against Islamists can be appealed in a process that could take years to reach a final verdict.

Egypt's constitution allows the president to issue pardons after a ruling is final.

El-Sisi has repeatedly said he cannot intervene in court procedures, stressing that doing so would undermine judicial independence.