Islamic State's Egypt affiliate on Wednesday urged followers to attack judges, declaring a new front in an Islamist militant insurgency in the world's most populous Arab state.
The leader of the group Sinai Province called for violence against judges in an audio statement posted on a prominent jihadist website.
Reuters could not confirm the authenticity of the recording.
A spate of attacks on judges suggests they are the latest targets of an insurgency centred in North Sinai that has killed hundreds of Egyptian soldiers and police in the past two years.
"It is wrong for the tyrants to jail our brothers," cleric Abu Osama al-Masry said, referring to judges. "Poison their food… surveil them at home and in the street… destroy their homes with explosives if you can."
Any full-blown campaign against judges could spell trouble for President Abdel Fattah al-Sisi, who as army chief removed the Muslim Brotherhood from power in mid-2013 after mass protests against its rule.
Sisi has only just managed to deliver a degree of stability to Egypt after years of political upheaval triggered by an uprising in 2011 that toppled autocrat Hosni Mubarak.
MASS DEATH SENTENCES
Although the judiciary says it is independent of the government and military, some of Egypt's judges have drawn accusations of blatant bias by handing down lengthy jail terms and mass death sentences against Islamists.
The recording appeared days after a court's decision to seek the death penalty for Morsi and follows the state's execution of six members of Sinai Province for an attack on soldiers in Cairo last year.
"The justices have been central to the repressive strategy the Egyptian government has pursued since the July 2013 coup," said Steven Cook, Mideast expert at the Council on Foreign Relations in Washington.
"The combination of the state's repressive tactics, mass jailings, death sentences and now the insurgency's call to kill judges makes it a toxic brew that will likely lead to an escalation of violence."
So far, Sinai Province has focused its bombing and shooting attacks on members of Egypt's security forces, who mounted the country's toughest crackdown on Islamists after Morsi's ouster.
Hundreds of Muslim Brotherhood supporters were killed in Cairo protest camps and thousands of others were arrested.
Cairo makes no distinction between the Brotherhood and ultra-hardline Sunni groups such as Islamic State, which has seized large swathes of Iraq and Syria and is boosting its presence in Egypt's neighbour Libya.
The Brotherhood says it is a peaceful movement still determined to return to power through street protests even though its top leaders are in prison.
Sisi has repeatedly called on Arab and Western states to mount a comprehensive military and ideological campaign to counter what he calls the existential threat posed by militants.
In a move that also put the spotlight on the justice system and the struggle against militancy, Egypt appointed a hardline judge and outspoken critic of the Brotherhood as justice minister on Wednesday.
Ahmed el-Zend, a former appeals court judge, has in contrast to his predecessor been publicly outspoken in his criticism of the Brotherhood, which was banned as a terrorist organization.
His appointment was decried by a leading opposition figure as a disaster for justice in Egypt, a strategic U.S ally that has faced off against militancy for decades.
"The appointment of someone like Ahmed el-Zend sends a clear message that the confrontation with the Brotherhood and Islamists in general will continue and perhaps even intensify," said Shadi Hamid, fellow at the Brookings Institution.
"Any kind of hope that the regime would start to pull back and lessen the degree of repression doesn't seem likely."
