Egypt has executed nine men convicted of killing the country's top public prosecutor, Hisham Barakat, in 2015.
The men were among 28 sentenced to death for their alleged involvement in the car bomb attack that targeted Barakat's convoy in the capital, Cairo.
Amnesty International said they were convicted after a grossly unfair trial marred by allegations of torture.
Their executions, the human rights group added, were "a testament to the magnitude of injustice in the country".
Egyptian criminal courts have sentenced hundreds of people to death in cases stemming from alleged political violence since July 2013, when the military overthrew the country's first democratically elected president, Mohammed Morsi.
The Court of Cassation has overturned many of the sentences, but 15 people have now been executed so far this year alone.
Three were convicted over the murder of a senior police officer in Cairo in 2013 and three others over the murder of a judge's son in Mansoura in 2014. Amnesty International said their trials were also marred by torture allegations.
The government blamed Morsi's Muslim Brotherhood and Gaza-based Hamas movement for Barakat's killing, although both denied they were involved.
Several of the men hanged on Wednesday alleged that they were tortured by security personnel to get confessions.
One of them, Mahmoud al-Ahmadi, was filmed telling a judge at a hearing: "Give me an electric probe and I'll make anyone confess to assassinating [the late President Anwar] Sadat.
"We have been electrocuted so much we could power Egypt for 20 years."
Najia Bounaim of Amnesty International said in a statement: "By carrying out the executions of these nine men today Egypt has demonstrated an absolute disregard for the right to life.
"The international community must not stay silent over this surge in executions. Egypt's allies must take a clear stand by publicly condemning the authorities' use of the death penalty, the ultimate cruel, inhuman and degrading punishment."