Three journalists have been killed and three others wounded in Baghdad after they came under fire on Tuesday, bringing the media death toll in Iraq to 12.
Journalists have become victims of the war they were sent to cover
Two cameramen, working for Reuters and Spain's Telecinco, were killed when a shell hit the hotel which houses hundreds of foreign journalists. There is video footage of an American Abrams tank firing at the building.
Earlier, a correspondent for the Arabic TV broadcaster al-Jazeera was killed when US missiles hit the network's office.
The US Defense Department has expressed regret for the deaths of journalists, but said American forces were acting in self-defence, having encountered small-arms fire coming from the direction of the hotel.
Chief spokeswomen Victoria Clark said she had repeatedly warned news organisations that correspondents were "not safe in a war zone".
A war zone is a dangerous place. We continue to warn news organisations... you should not be there
Pentagon spokeswoman Victoria Clark
The International Federation of Journalists (IFJ) - which represents hundreds of thousands of journalists worldwide - issued a statement on Tuesday condemning both sides in the conflict.
BBC correspondent Rageh Omaar, who was in the Hotel Palestine the time, said video footage filmed by both a French television crew and the BBC had picked up no sounds of fire coming from the hotel in the 20 or 30 minutes before the blast.
The international press corps in Baghdad held a candle-lit vigil for their dead colleagues outside the hotel on Tuesday night.
Initially, US military officials expressed regret at the incident, saying one of their tanks had fired on the building in response to sniper and rocket fire.
"A tank was receiving small arms fire... from the hotel and engaged the target with one tank round," General Buford Blount, commander of the US 3rd Infantry Division in Baghdad, told Reuters.
But the US military later refused to confirm whether it had been the tank shell that had caused the journalists' deaths.
MEDIA DEATHS IN IRAQ
8 April: Jose Couso (Telecinco, Spain)
8 April: Taras Protsyuk (Reuters, UK)
8 April: Tareq Ayoub (al-Jazeera, Qatar)
7 April: Christian Liebig (Focus, Germany)
7 April: Julio Anguita Parrado (El Mundo, Spain)
6 April: David Bloom (non-combat related death) (NBC, US)
6 April: Kamaran Abdurazaq Muhamed (BBC, UK)
4 April: Michael Kelly (Washington Post, US)
2 April: Kaveh Golestan (BBC, UK)
30 March: Gaby Rado (ITN, UK)
22 March: Paul Moran (ABC, Australia)
22 March: Terry Lloyd (ITN, UK)
Spain says it is demanding an explanation from Washington, while Greece - which holds the rotating presidency of the European Union - condemned the attack and said it would ask the US to guarantee the safety of journalists.
Spanish Defence Minister Federico Trillo called on journalists in Baghdad to abandon the Iraqi capital, reported the Spanish news agency Efe.
Mr Trillo reportedly warned media heads that journalists could be used by the Iraqis as "military objectives".
Reuters said Ukrainian cameraman Taras Protsyuk died and a reporter, a photographer, and a technician were wounded when the building was hit.
"Taras' death, and the injuries sustained by the others, were so unnecessary," said Reuters' editor-in-chief Geert Linnebank.
Spanish television network Telecinco said cameraman Jose Couso died during surgery for injuries sustained to his leg, chest and jaw.
Al-Jazeera said its correspondent Tareq Ayoub died and a cameraman was injured when two missiles hit its office, virtually destroying it.
US military officials said the building was struck by mistake. In November 2001, American warplanes mistakenly bombed the offices of the same broadcaster in Kabul, Afghanistan during the US-led campaign to oust the Taleban.
Reporting from Iraq is fraught with danger
"It is something we all regret. But I don't believe that it is possible that it was deliberate," US State Department spokesman Nabil Khoury said.
But the Reporters Without Borders pressure group said al-Jazeera had been careful to inform the Americans of the exact location of its offices.
The Committee to Protect Journalists, a watchdog, criticised both attacks in a letter to US Defence Secretary Donald Rumsfeld, saying they violated Geneva conventions.
Both demanded immediate investigations.
Al-Jazeera told the BBC it was determined to maintain a presence in Baghdad, despite the tragedy.
Abu Dhabi television said its Baghdad bureau was also hit by US bombing.
According to the news agency AFP, a correspondent there issued an SOS, saying its reporters were "surrounded" in a military zone and appealing to the Red Cross to pull them out of the area.
Two "embedded" foreign journalists died on Monday in an Iraqi missile attack, bringing the media death toll to five in less than 24 hours.
Julio Anguita Parrado who worked for Spain's El Mundo newspaper and Christian Liepig, who was covering the war for German weekly Focus, were travelling with US forces when they came under attack.