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A man in the US has been arrested after threatening to shoot a Republican congresswoman who supports President Donald Trump.

Steve Martan allegedly called Martha McSally's office several times, making death threats and saying she should be careful if she visited Tucson, Arizona.

FBI officials traced the calls back to his mobile phone.

When they visited him, he said he was "venting frustrations" with Ms McSally's votes in support of Mr Trump.

A complaint filed with a local court alleges that Mr Martan called the congressional office three times, using expletives and making general threats such as saying her days were "numbered", as well as threats to wring Ms McSally's neck or shoot her.

Ms McSally said the threats were "especially sickening" in view of the shooting of another congresswoman, Gabrielle Giffords, in Tucson six years ago.

Six people died in that attack in 2011, and a total of 13 were wounded.

Ms Giffords survived the attack but spent time in an induced coma and suffered serious brain injury that left one of her arms paralysed and affected her speech. The man who shot her pleaded guilty on 19 counts of murder and attempted murder, and is serving seven life sentences plus 140 years.

Ms Giffords has issued a statement saying that the threats against Ms McSally were "reprehensible and deeply disturbing".

Ms McSally said: "We can disagree about issues and policies. We should have robust debates about the future of our country. But threats of violence cross a clear line."

Mr Martan has been released from custody, but will have to wear an electronic tag and is not permitted to contact Ms McSally or carry a gun, a local newspaper reported.

He is only allowed to leave the house for his work at a school and for his governmentally-mandated mental health programme.