Giulio Regeni, a 28-year-old doctoral student who had been researching trade unions, disappeared in Cairo on January 25.
His badly mutilated body was found over a week later by the side of a road on the city's outskirts.
The killing has caused tensions between Italy and Egypt -- earlier this month, Rome recalled its ambassador in protest at the lack of developments in the probe.
The Foreign Office in London issued a statement late Monday on the killing of Regeni, who had reportedly lived in Britain for a decade.
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"Three months after Mr Regeni's death, we are disappointed by the limited progress made in the case and are concerned that Italy has not found the cooperation that Egypt has provided to them to be sufficient," it said.
The statement added that, while allegations that Egyptian security forces were behind the killing were "unproven", "we urge the Egyptian authorities to consider every possible scenario as they investigate."
Over 11,000 people have signed a petition urging the British government to ensure that "a credible investigation of this extrajudicial killing is carried out".
Egypt's presentation of a theory that a criminal gang carried out the murder has been received with extreme scepticism in Italy and helped fuel public anger over the case.