CAIRO: Egypt's Interior Ministry said on Thursday that security forces had retrieved a bag and passport belonging to murdered Italian student Giulio Regeni that was in the possession of a criminal gang impersonating policemen who had been killed in a shootout.

Human rights groups have said torture marks on Regeni's body, which was dumped on the side of the road, indicated he died at the hands of Egyptian security services, an allegation the government has strongly denied.

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

The Interior Ministry said security forces had targeted the criminal gang which had Regeni's bag and that it had "specialized in impersonating police officers, kidnapping foreigners and forcibly robbing them".

It said that a red handbag bearing the Italian flag was found, and inside it was Regeni's passport and other items such as a visa card two cell phones and a "feminine wallet" with the word love on it and a dark substance resembling hashish.

"A highly skilled investigation team was formed to uncover the mystery of several reported forced robberies and incidents of impersonating police officers," said the ministry in a statement.

The ministry named what it identified as four ring leaders of the gang; Tarek Saad Abd El-Fatah, 52, described as a dangerous offender guilty of fraud and other offences, and his son Saad Tarek Saad, 26.

Also mentioned were Mustafa Bakr Awad, 60, charged with fraud and 20 varied offences, and Salah Ali Sayed, 40, who the ministry said had committed similar crimes.

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

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.

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.

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 had told Reuters.

The findings were 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.

Interior Ministry spokesmen declined comment on this matter.