Egyptian police have increased security at the homes of prominent liberal opponents of the government, after a hardline cleric called for their deaths, the interior ministry says.
The killing on Wednesday of Shokri Belaid, an outspoken critic of Tunisia's Islamist-led government, has sent tremors through Egypt.
General Hani Abdel Latif, an interior ministry spokesperson, said on Thursday that security authorities will increase patrols in residential areas where opposition leaders live.
"Arab Spring" uprisings in both countries swept away veteran authoritarian rulers in 2011, but their ousters have been followed by two years of political turmoil that have exposed divisions between religious political parties and their secular opponents.
On the same day, Mohamed ElBaradei, a liberal Egyptian politician, revealed that Mahmoud Shaaban, a hardline religious cleric, had called for his death.
Shaaban appeared on a religious television channel and said leaders of Egypt's main opposition coalition would get a death sentence under Islamic law.
He specifically mentioned ElBaradei, a Nobel Peace Prize laureate, and former presidential candidate Hamdeen Sabahy.
Presidency condemns threats
President Mohamed Morsi, a member of the Muslim Brotherhood, which has dominated democratic elections since mass protests ousted President Hosni Mubarak in 2011, condemned such comments as tantamount to "terrorism".
He stood by his earlier assertion, however, that the country's liberal opposition was inciting unrest.
"It is strange that some [in Egypt] advocate political violence and incite it while others, who claim to speak in the name of religion, allow 'killing' on the basis of political differences, which is terrorism itself," a statement from Morsi's office said.
"The presidency affirms its complete rejection of hate speech that falsely uses religion, and of which religion is innocent, and calls on national forces, religious institutions and leading thinkers to stand in a united front to confront this unacceptable language of incitement."
Shaaban's statement has been condemned across the board by all major political and religious parties in Egypt.
Prime Minister Hisham Kandil said on his Facebook page the cabinet was looking into legal steps it could take against "all those who issue or spread edicts or fatwas inciting violence".
Belaid's assassination in the Tunisian capital Tunis "sounds danger alarms from Tunisia to Cairo, and warns of the cancerous growth of terrorist groups cloaked by religion and carrying out a plot to liquidate the opposition morally and physically", Egypt's main opposition coalition, the National Salvation Front, said in a statement.