US President Donald Trump has demanded an investigation into whether his 2016 presidential campaign was infiltrated or surveilled by the FBI or the department under the Obama administration.

Mr Tump’s pronouncement on Monday morning (AEST) followed a series of seven tweets in which he denounced the federal investigation into whether his campaign worked with Russia to sway the election as a “witch hunt”.

“I hereby demand, and will do so officially tomorrow, that the Department of Justice look into whether or not the FBI/DOJ infiltrated or surveilled the Trump Campaign for Political Purposes – And if any such demands or requests were made by people within the Obama Administration!” Mr Trump wrote on Twitter.

I hereby demand, and will do so officially tomorrow, that the Department of Justice look into whether or not the FBI/DOJ infiltrated or surveilled the Trump Campaign for Political Purposes – and if any such demands or requests were made by people within the Obama Administration!

— Donald J. Trump (@realDonaldTrump) May 20, 2018

Earlier, Mr Trump, without naming Special Counsel Robert Mueller, repeated his criticism of the probe as politically motivated.

He reprised his attacks on Hillary Clinton, his Democratic challenger in 2016 and maintained that the Democrats were not submitted to the same scrutiny by the FBI.

He said “Republicans and real Americans should start getting tough on this Scam”.

Mr Trump also implied that the special counsel investigation of whether foreign governments tried to influence the presidential campaign was designed to hurt Republicans in the November congressional elections.

“Now that the Witch Hunt has given up on Russia and is looking at the rest of the World, they should easily be able to take it into the Mid-Term Elections where they can put some hurt on the Republican Party,” he wrote.

“The Witch Hunt finds no Collusion with Russia – so now they’re looking at the rest of the World. Oh’ great!”

-with AAP