Two major international press watchdogs have denounced three US military strikes in Baghdad o­n Tuesday that killed three journalists and wounded many more.

Amnesty International also expressed concerns about the attacks, which, according to US Central Command, came in response to ''significant enemy fire''.

''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-defence,'' Pentagon spokesperson Victoria Clarke told reporters Wednesday.

But journalists at two of the sites said they had seen no shooting by Iraqi forces from the buildings that housed the media workers when they were attacked by US forces.

Death toll

According to the New York-based Committee to Protect Journalists (CPJ), US air strikes severely damaged the Baghdad office of the Al-Jazeera satellite network, killing journalist Tareq Ayoub (photo) and injuring cameraman Zouhair al-Iraqi.

Just moments later another explosion, reportedly from US artillery, damaged the offices of Abu Dhabi TV less than 2km away, trapping as many as 30 journalists in the debris.

In the third incident, a US tank fired o­n the Palestine Hotel, which serves as the main base for international journalists covering the war from Baghdad, killing two journalists and wounding at least three others.

Reuters cameraman Taras Protsyuk and a colleague from Spain's Telecinco television, Jose Souso, were killed in the blast and at least three other journalists were wounded, according to CPJ.

Pentagon officials insisted that they had not targeted any of the offices, but Paris-based Reporters Without Borders (RSF) called o­n US Defence Secretary Donald Rumsfeld (photo) to provide evidence that none of the attacks was a deliberate attempt to intimidate or retaliate against journalists who are covering the war.

''We are appalled at what happened because it was known that both (the Palestine Hotel and the Al-Jazeera office) contained journalists,'' said RSF secretary-general Robert Menard.

''We are concerned at the US army's increasingly hostile attitude towards journalists, especially those non-embedded in its military units.''

In its statement, CPJ agreed that the incidents were ''particularly troubling'' because the location of both Arab television offices and the Palestine Hotel were widely known.

In addition, before hostilities broke out last month both Al-Jazeera and Abu Dhabi TV provided specific co-ordinates of their Baghdad offices to Clarke's office to prevent mistakes. CPJ called o­n Rumsfeld to undertake an ''immediate and thorough investigation'' into the incidents.

''The attack against Al-Jazeera is of particular concern since the stations' offices were also hit in Kabul, Afghanistan in November 2001,'' the group said in a letter faxed to Rumsfeld late Tuesday.

At that time, the Pentagon insisted that the Al-Jazeera office in the Afghan capital was a ''known al-Qaeda facility'', and that it did not know that the television network operated from there.

Breach of conventions

Amnesty and CPJ said that the Baghdad incidents appeared to violate the Geneva Conventions providing that military operations must be ''limited strictly to military objectives''.

Said Amnesty: ''Although the US has claimed it is going to 'great lengths to minimise civilian casualties and damage to civilian facilities', it has declared Baghdad a 'combat zone' and has fired o­n media facilities. Challenged to explain attacks o­n buildings occupied by international media, US authorities have offered shifting explanations.

''Unless the US can demonstrate that the Palestine Hotel had been used for military purposes, it was a civilian object protected under international humanitarian law that should not have been attacked. If it had demonstrably been used for military purposes, it should not have been attacked by a tank shell, clearly incapable of careful targeting in this case.''

Journalists at the hotel said they had neither seen nor heard firing from the building before the attack, while CPJ said that even if firing had taken place from the building, the response of US forces was ''disproportionate and thereby violated international humanitarian law''.

Of particular concern to the New York-based group was the impression left by Pentagon spokesmen, such as Brig. Gen. Vincent Brooks (photo), who said Tuesday that non-embedded journalists - those not travelling under the protection and control of coalition forces - operate at their own risk and that US forces bear no responsibility for protecting journalists who are operating independently in Iraq.

Clarke reiterated that point Wednesday: ''We've had conversations over the last couple of days (with) news organisations eager to get their people unilaterally into Baghdad. We are saying it is not a safe place; you should not be there.''

CPJ, in its letter to Rumsfeld said: ''We remind you that journalists are civilians and protected under international humanitarian law and cannot be deliberately targeted.

"While we recognise the important role of embedded reporters, the Geneva Conventions also contemplate the presence of non-embedded, or 'civilian', journalists o­n the battlefield, and the US military has an obligation to avoid harming them.''

CPJ, RSF, the International Press Institute, and the International Federation of Journalists last week protested the US bombing of Iraqi state television headquarters in Baghdad, which, according to the Pentagon, was being used as a command-and-control facility for the Iraqi armed forces.

The groups also questioned the March 29 and 30 bombings of the Information Ministry headquarters, where foreign news media are based.

'Cruel' treatment

CPJ and other watchdogs have also charged that reporters who were not ''embedded'' had been poorly treated by US forces in southern Iraq.

Four journalists - two Israelis and two Portuguese - were arrested March 25 by US. troops, accused of spying, and detained in a jeep for 36 hours without access to outside communications, despite providing proof of their press affiliations. o­ne of the four, Luis de Castro of Portugal, says he was beaten badly by US soldiers.

''The US soldiers said we were terrorists and spies and treated us as such,'' said Dan Scemama, who works for Israel Channel o­ne TV. "They want all journalists in Iraq to have o­ne of their liaison officers with them to supervise the footage they are broadcasting. There is no doubt that this is why they treated us so cruelly.''

In a related development Tuesday, the San Francisco-based Association for Progressive Communications (APC) protested the targeting by so-called ''patriotic hackers'' of the English-language Al-Jazeera website, which was launched March 27.

APC said the site had been virtually impossible to access because hackers re-directed viewers to another page that featured the image of the U.S. flag and a message proclaiming 'Let Freedom Ring'.

London-based Index o­n Censorship last month awarded Al-Jazeera its free-expression prize for its ''courage in circumventing censorship and contributing to the free exchange of information in the Arab world.