BAGHDAD, Iraq - Nursing an injured shoulder, an Italian journalist held by Iraqi insurgents returned to Italy on Saturday, a day after she came under gunfire from U.S. troops while on her way to freedom. An intelligence agent who had helped negotiate her release was killed.

President Bush expressed regret and promised to investigate the incident, which happened at a checkpoint in Baghdad. The military said U.S. soldiers, not knowing the car was carrying journalist Giuliana Sgrena, fired after it failed to slow down.

But Bush's phone call Friday to Prime Minister Silvio Berlusconi did little to assuage anger In Italy, which has been holding its breath over Sgrena's fate for weeks. The shooting was likely to set off fresh protests against Berlusconi for keeping 3,000 troops in Iraq despite strong opposition.

"Another victim of an absurd war," said Alfonso Pecoraro Scanio, leader of the Green Party.

A communist senator called for a protest Saturday in front of the U.S. Consulate in Milan.

Sgrena left Iraq after she was discharged from an American military hospital in Baghdad where she had been treated for shrapnel in the shoulder.

Berlusconi was among those at the airport to greet Sgrena on Saturday. She had to be helped out of the small, private jet and was placed in a waiting ambulance. She was expected to be transferred to a military hospital for an operation on her collarbone later Saturday, the news agency Apcom said.

Sgrena, 56, was abducted Feb. 4 by gunmen who blocked her car outside Baghdad University. Last month, she was shown in a video pleading for her life and demanding that all foreign troops - including Italian forces - leave Iraq.

Friday's shooting occurred shortly after her release. It was about 9 p.m. in Baghdad at the time.

The U.S. military said the car was speeding as it approached a coalition checkpoint in western Baghdad on its way to the airport. It said soldiers shot into the engine block only after trying to warn the driver to stop by "hand and arm signals, flashing white lights, and firing warning shots."

The intelligence agent was killed when he threw himself over Sgrena to protect her from U.S. fire, Apcom quoted Gabriele Polo, the editor of the leftist Italian newspaper Il Manifesto, as saying. Sgrena works for Il Manifesto.

Berlusconi identified the dead intelligence officer as Nicola Calipari and said he had been at the forefront of negotiations with the kidnappers. The prime minister said Calipari had been involved in the release of other Italian hostages in Iraq in the past.

The Americans said two people were wounded, but Berlusconi said there were three - Sgrena and two intelligence officers. One of the officers was in serious condition, according to the Apcom news agency in Italy.

Insurgents have repeatedly attacked checkpoints, and soldiers have often fired on cars that don't obey commands to stop or slow down.

Berlusconi said he had been celebrating Sgrena's release with the editor of Il Manifesto and Sgrena's boyfriend, Pier Scolari, when he took a phone call from an agent who informed them of the shooting.

"It's a shame that the joy we all felt was turned into tragedy," Berlusconi said.

The shooting came as a blow to Berlusconi, who continues to face huge protests over his support for the Iraq war and his refusal to withdraw Italian troops. Sgrena's newspaper was a loud opponent of the war.

"It's incredible that a man who was busying himself with the difficult task of saving a life was killed by those who say they are in Iraq to safeguard the life of civilians," said Piero Fassino, leader of the Democratic Party of the Left.

Bush called Berlusconi and expressed regret about the incident, Bush spokesman Scott McClellan told reporters Friday night.

"The president assured Prime Minister Berlusconi it would be fully investigated," McClellan said.