"My understanding is, again, context, we are at war, there is fighting going on in Baghdad, our forces came under fire, they exercised their inherent right to self-defense," said Pentagon spokeswoman Victoria Clarke.

In private, however, some US defense officials quoted Wednesday in The Washington Post acknowledged that the tanker who fired on the hotel may have acted hastily, possibly mistaking the journalists' cameras for weapons.

Television reporters from Reuters and Spain's Telecinco were killed Tuesday in the single shot fired into an upper floor of the Palestine Hotel, and an Al-Jazeera correspondent was killed in a separate missile attack on the Arabic news network's offices in downton Baghdad.

The dead were identified as Taras Protsyuk, a Ukrainian cameraman with Reuters, Jose Couso from Spanish network Telecinco, and Tareq Ayub, the Al-Jazeera correspondent.

The attacks brought calls from journalists groups for an investigation and put in question US assertions that US forces were taking utmost care to avoid civilian casualties.

Spain and Portugal have called on their journalists covering the war to leave Baghdad.

The commander of the US Army's 3rd Infantry Division, General Buford Blount, told reporters at the Baghdad airport after the attack that the tank took action after coming under small arms and rocket-propelled grenade fire from the hotel.

The US Central Command issued a statement asserting that US forces came under "significant enemy fire" at both the hotel and the Al-Jazeera offices, and blamed the Iraqi regime for using civilians as cover for military operations.

But the Palestine Hotel was widely known to house journalists covering the war, and reporters there said they did not hear fire directed at the tank, which was positioned at the entrance to a bridge about 600 meters (yards) northwest of the hotel.

A cameraman from France 3 television filmed the tank as it turned and raised its main gun, waited for about two minutes and then fired.

"It had been very quiet for a moment. There was no shooting at all. Then I saw the turret turning in our direction and the carriage lifting. It faced the target," said Herve De Ploeg, who filmed the scene.

"It was not a case of instinctive firing," he said.

The shell struck a hotel balcony where journalists were watching an ongoing battle across the river.

Major General Stanley McChrystal, vice director of operations of the Joint Staff, noted that US forces had fought their way into Baghdad.

"You put yourself in their position. They had the inherent right of self-defense," he said.

"When they are fired at, they have not only the right to respond, they have the obligation to respond to protect the soldiers with them and to accomplish the mission at large," he said.

"So when they receive fire, and regardless of how specific they can be of where it came from, and normally they're pretty good at it, they have that right and they have that responsibility.

Clarke said news organizations had been warned of the dangers in Baghdad.

"We continue to warn people, we continue to warn news organizations about the dangers," she said.

"We've had conversations over the last couple of days, news organizations eager to get their people unilaterally into Baghdad. We are saying it is not a safe place, you should not be there."

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