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Former Alaska governor Sarah Palin has attacked as a "blood libel" suggestions that political rhetoric contributed to Saturday's fatal shootings in Arizona.

Ms Palin, a possible 2012 presidential runner, hit out at commentators' "irresponsible statements" laying "blame for this terrible event".

Her came as new details emerged about the attack, in which six were killed and morethan a dozen wounded.

Jared Loughner, 22, has been jailed pending trial for the attack.

"Especially within hours of a tragedy unfolding, journalists and pundits should not manufacture a blood libel that serves only to incite the very hatred and violence they purport to condemn," she said in the video released on her Facebook page. "That is reprehensible."

The video statement from the 2008 vice-presidential candidate came hours before President Barack Obama is set to fly to Arizona to attend a service honouring victims of the shooting.

Some commentators have suggested increasingly vitriolic political rhetoric in the US may have contributed in some way to the attack, with some specifically criticising Ms Palin for using an online graphic containing crosshair symbols that marked targeted Democratic districts in the recent US mid term elections.

Among the districts targeted was that of Gabrielle Giffords of Arizona, who was gravely injured in Saturday's attack at a constituency outreach meeting in a Tucson shopping centre.

In her statement on Wednesday, Ms Palin rejected any suggestion that the political climate had contributed to the act.

"Acts of monstrous criminality stand on their own," Ms Palin said.

"They begin and end with the criminals who commit them, not collectively with all the citizens of a state, not with those who listen to talk radio, not with maps of swing districts used by both sides of the aisle, not with law-abiding citizens who respectfully exercise their First Amendment rights at campaign rallies, not with those who proudly voted in the last election."

Pro-Israel lobby group J Street said in a statement that it hoped Ms Palin would retract her comment and choose a "less inflammatory choice of words".

"The term 'blood libel' brings back painful echoes of a very dark time in our communal history when Jews were falsely accused of committing heinous deeds," the group said.

Six were killed in the attack, including a federal judge and a nine-year-old girl, and more than a dozen wounded. Ms Giffords was shot in the head and remains in critical condition, though doctors have said she is able to breathe on her own and appears slowly to be recovering.

Mr Loughner has been charged with several federal crimes over the shooting, and could face the death penalty. In an initial court appearance on Monday he was remanded in custody pending trial.

The US House of Representatives on Wednesday took up a resolution honouring Ms Giffords and other victims of the attack, with House Speaker John Boehner fighting back tears as he spoke about his ailing colleague.

"Our hearts are broken but our spirit is not," the Ohio Republican said.

The resolution declares the House "stands firm in its belief in a democracy in which all can participate and in which intimidation and threats of violence cannot silence the voices of any American."

The House had postponed a vote on a divisive effort to repeal President Barack Obama's healthcare plan in order to take up the resolution.

Also on Wednesday, the House sergeant-at-arms held a security briefing for lawmakers, advising them to co-ordinate public events in their constituencies with local police.

While some US legislators have called for stricter gun control in the wake of Saturday's shooting, Rep Trent Franks said: "I wish there was one more gun that day in the hands of a responsible person."

Meanwhile, fresh details have emerged of the hours leading up to the fatal attack. Among those, Arizona police have said an officer stopped Mr Loughner for speeding, but let him go with a verbal warning.