The shooting on the road to Baghdad airport late on Friday threatened to cast a pall over relations between Rome and Washington, which are close allies in the Iraq conflict.
Sgrena, the 56-year-old correspondent of the daily ll Manifesto, told Italian investigators the US troops' intense fire had been in no way justified by the speed of her car, ANSA news agency said.
"Our vehicle was running at normal speed which could not be misunderstood," she said, rejecting US fears of a possible suicide attack.
"It wasn't a checkpoint but a patrol which immediately opened fire after they trained their light on us," Sgrena said on her return from Iraq .
The US military said on Friday Sgrena's convoy had ignored signals to stop, and that US soldiers had waved their hands and arms, flashed white lights and fired warning shots in a failed attempt to get the vehicle to stop.
US President George Bush has promised a full investigation into the incident.
Protestors in Rome called for
Meanwhile, about 100 protesters gathered outside the US embassy here and called for a US withdrawal from Iraq, Italian Prime Minister Silvio Berlusconi's resignation and support for the family of intelligence officer Nicola Calipari.
They carried a banner reading: "Bush has changed: now he even kills Italians".
Sgrena, her left shoulder in a bandage, flew into Rome on a government plane on Saturday morning and was immediately rushed to Celio military hospital where she will undergo surgery within the next few days. She had been given emergency treatment in a US military hospital in Baghdad.
Scolari bitterly criticised the US
account of the firing on Sgrena
Her companion, who travelled with her from Baghdad, levelled serious accusations at the US troops involved in the incident, saying the shooting had been deliberate.
"The Americans and Italians knew about (her) car coming," Pier Scolari said on leaving Celio hospital.
"They were 700 metres from the airport, which means that they had passed all checkpoints."
In a related incident, the Paris-based press watchdog group Reporters Without Borders on Saturday called for a UN investigation into US military conduct in the Sgrena affair.
"A thorough investigation must be quickly carried out by the United Nations into this blunder with tragic consequences," said a statement by the head of the group, Robert Menard.
He said the investigation must not be carried out by the US Army, which would risk "exonerating the military".
"We demand to know the full truth about this distressing affair," Menard's statement said.