An Egyptian forensics official has told the public prosecutor's office the autopsy he conducted on an Italian student showed he was interrogated for up to seven days before he was killed, two prosecution sources said.

The findings are the strongest indication yet that Giulio Regeni was killed by Egyptian security services because they point to interrogation methods such as burning with cigarettes in intervals over several days, which human rights groups say are the hallmark of the security services.

In the past, the Interior Ministry has rejected accusations about human rights abuses.

The prosecution sources said Hisham Abdel Hamid, Director of the Department of Forensic Medicine, gave his findings during questioning as an expert by officials in the public prosecutor's office last week.

"We asked Hisham Abdel Hamid to appear before the prosecutor's office for questioning, to ask him questions about the autopsy," an investigator in the prosecutor's office told Reuters, adding that Abdel Hamid was accompanied by two associates who also took part in the autopsy.

"Abdel Hamid said during the questioning that the wounds on the body occurred over different intervals of between 10-14 hours. That means that whoever is accused of killing him was interrogating him for information."

The main Interior Ministry spokesman was not available for comment. Another Interior Ministry spokesman, asked by Reuters to comment on the findings, said: "I know nothing about this matter."

A source in the Department of Forensic Medicine confirmed Abdel Hamid had been questioned. Reuters reached Abdel Hamid by telephone but he declined to comment.

Regeni, 28, disappeared on Jan. 25, the anniversary of the 2011 uprising that ended former President Hosni Mubarak's 30-year rule.

Regeni had written articles critical of the Egyptian government, the Italian newspaper that published them said.

The broken corpse of the Cambridge University student, who was researching the rise of independent labour unions following the 2011 revolt, was found in a ditch on the side of a motorway on Feb. 3.

Egyptian forensics and prosecution officials have said his body showed signs of torture and that he was killed by a blow with a sharp object to the back of the head.

"The autopsy report shows a number of injuries at one time; and there are a number of other injuries later and other injuries a third time," said another investigator in the public prosecutor's office, summarising Abdel Hamid's statements.

"The wounds and fractures occurred at different times in intervals during a period of about five to seven days."

Tensions with Italy

The case has put a spotlight on alleged police brutality in Egypt, a strategic ally of the United State and other Western powers.

Mourners hold messages at a vigil for slain Italian graduate student Giulio Regeni, in front of the Italian embassy in Cairo, Egypt, on Feb. 6. (Amr Nabil/Associated Press)

Shopkeepers in Regeni's neighbourhood of Cairo said there were no signs that police in the area had been questioning people since his disappearance or death.

Rights groups accuse the police of widespread abuses against Egyptians since the army toppled Egypt's first freely elected president in 2013.

Such actions against foreigners are not common.

Italy has said Egyptian investigators should hand over the evidence they have uncovered on Regeni's death. Egypt invited Italian investigators to take part in the investigation, but judicial sources in Rome say the collaboration has been limited because not enough information was shared.

A second autopsy in Italy "confronted us with something inhuman, something animal", Italian Interior Minister Angelino Alfa has said without elaborating further.

The case has created tensions between Egypt and Italy.

Egypt's interior ministry has said possible motives for the killers included criminal activity or the desire for revenge "due to personal reasons".

Italian judicial sources say an Italian team in Cairo has not received any information of value from their Egyptian counterparts. "They have given us nothing," a judicial source told Reuters.

Full details of the Italian autopsy on Regeni are due to be handed over to the investigators later on Monday.