Egypt has rejected claims that security forces were involved in the case of Italian Giulio Regeni, who was found dead bearing signs of torture after disappearing in Cairo last month.
Regeni, a University of Cambridge PhD student, disappeared on January 25 and was found dead on February 3 in a ditch in a Cairo suburb.
"This did not happen," Magdy Abdel Ghaffar, Egypt's interior minister, said on Monday when a reporter asked if Regeni had been arrested by the police.
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"It is completely unacceptable that such accusations be directed" at the interior ministry, he said.
"This is not Egyptian security policy - Egyptian security has never been accused of such a matter."
Critics in Egypt accuse the interior ministry and several policemen of using excessive force. Several policemen are being tried for torture-related deaths.
The ministry says these are isolated cases.
After the student's remains were repatriated at the weekend, an Italian autopsy concluded that he was killed by a violent blow to the base of the skull, having already suffered multiple fractures all over his body.
Rights activists and several opposition groups say Regeni, who was doing research on Egyptian trade union movements, had been arrested by the police and tortured.
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The diplomatic community and the Italian media have also raised the possibility of torture.
Abdel Ghaffar further said that Regeni had not been arrested and that his death was "certainly a criminal act".
He said no suspects had yet been arrested.
"We are still in the phase of information-gathering. This matter needs some time," he said.
Global rights groups have regularly denounced mysterious disappearances of activists and the torture and beating of detainees in Egyptian detention centres.
President Abdel Fattah el-Sisi has urged security forces to restrain themselves after several cases of people dying in custody emerged in recent months.
Regeni went missing in central Cairo while on the way to meet a friend on January 25, the fifth anniversary of the start of the uprising against longtime autocrat Hosni Mubarak.
On the anniversary Cairo was quiet, with police deployed across the city to prevent any demonstrations.