US President Donald Trump has sacked his secretary of state Rex Tillerson and replaced him with a 'Christian zealot' Mike Pompeo, who is currently head of the CIA.

The shock announcement, made on Trump's Twitter account this afternoon, came after Tillerson singled out Russia for criticism over the attack on a former spy in Salisbury.

British prime minister Theresa May said it was 'highly likely' Russia was responsible but earlier in the day the White House appeared more reluctant to place the blame on Moscow.

'It sounds to me like it could be Russia,' Trump told reporters outside the White House on Tuesday. 'As soon as we get the facts straight we will condemn Russia,' he said.

The tweet, where the president also nominated Gina Haspel to become the first woman director of the CIA, took Tillerson by surprise.

A state department spokesman, Steve Goldstein, said: 'The secretary did not speak to the president and is unaware of the reason, but he is grateful for the opportunity to serve, and still believes strongly that public service is a noble calling.'

The White House issued grateful statements from both Pompeo and Haspel.

'I am deeply grateful to President Trump for permitting me to serve as director of the Central Intelligence Agency and for this opportunity to serve as secretary of state,' Pompeo said. 'His leadership has made America safer and I look forward to representing him and the American people to the rest of the world to further America's prosperity.'

A senior White House official said: 'The president wanted to make sure to have his new team in place in advance of the upcoming talks with North Korea and various ongoing trade negotiations.' 

Who is Mike Pompeo?

Pompeo is a Tea Party Republican and a deeply conservative evangelical Christian with particularly strong views about Islam. He is a graduate of West Point and Harvard and former Republican congressman and is widely seen as more of a loyalist than Tillerson.

'This threat to America is from people who deeply believe that Islam is the way and the light and the only answer,' he said addressing a church in Kansas in 2014.

Noting terrorists only made up a minority of Muslims, he said: 'These folks believe that it is religiously driven for them to wipe Christians from the face of the earth.'

A former army captain, Pompeo said on religious television: 'Make sure that we know that Jesus Christ is our saviour and is truly the only solution for our world,'

Speaking in church on another occasion Pompeo said: 'America had worshipped other Gods and called it multiculturalism. We'd endorsed perversion and called it an alternative lifestyle.'

He is a close friend and ally to Frank Gaffney, Trump's far-right foreign policy adviser, who said adherence to Islamic law should be 'an impermissible act of sedition, which has to be prosecuted'.

Pompeo is a strong critic of both Barack Obama, who is said had an 'affinity' with ISIS and former secretary of state Hillary Clinton who he described as 'morally reprehensible'.

In a February 2015 interview, Gaffney asked Pompeo whether Obama has 'kind of an affinity for, if not the violent beheading and crucifixions and slaying of Christians and all that, but at least for the cause for which these guys are engaged in such activities.' In response Pompeo said: 'Frank, every place you stare at the president's policies and statements, you see what you just described.'

Shortly after the Boston bombings in 2013 he criticised Muslim leaders for their response.

'When the most devastating terrorist attacks on America in the last 20 years come overwhelmingly from people of a single faith and are performed in the name of that faith, a special obligation falls on those that the leaders of that faith,' he said on the House floor.

He added the 'silence of Muslim leaders has been deafening'. It 'has made these Islamic leaders across America potentially complicit in these acts', he said, and 'casts doubt upon the commitment to peace among adherents of the Muslim faith.'

Pompeo has also spoken in support of the CIA's use of torture.

'Our men and women who were tasked to keep us safe in the aftermath of 9/11 — our military and our intelligence warriors — are heroes, not pawns in some liberal game being played by the ACLU and Senator Feinstein,' Pompeo said in a statement in 2014 in response to a report that was critical of the CIA's use of torture. 'These men and women are not torturers, they are patriots. The programs being used were within the law, within the constitution, and conducted with the full knowledge [of] Senator Feinstein. If any individual did operate outside of the program's legal framework, I would expect them to be prosecuted to the full extent of the law.'