US President Donald Trump has claimed without evidence that newly released documents relating to the wiretapping of his onetime campaign adviser Carter Page "confirm with little doubt" that intelligence agencies misled the courts that approved the warrant.
But politicians from both parties say the documents don't show wrongdoing.
The documents have been at the centre of a political firestorm for months, as some Republicans have suggested that the FBI misrepresented evidence to obtain warrants to monitor Mr Page as they investigated possible collusion between the Russian government and a Trump aide.
Mr Trump made the claim in a series of tweets where he also took aim at defeated Democrat candidate Hillary Clinton and the Democratic National Committee, her party's governing body, saying the surveillance was "for the political gain of Crooked Hillary Clinton and the DNC".
Mr Page has denied being an agent of the Russian government and has not been charged with any crime.
Republicans have claimed that law enforcement officials had improperly obtained a warrant to monitor Mr page, accusing the FBI of abusing its intelligence powers, while Mr Trump called it an "illegal scam".'Collaborating and conspiring with the Russian Government'
The documents had remained out of public view until Saturday, when they were released under the Freedom of Information Act.
The 412 pages, mostly heavily redacted, included surveillance applications to the Foreign Intelligence Surveillance Court and warrants surrounding the investigation into Mr Page.
Visible portions of the heavily redacted documents show the FBI telling the court that Mr Page "has been collaborating and conspiring with the Russian government".
"The FBI believes that the Russian Government's efforts are being coordinated with Page and perhaps other individuals associated with [Mr Trump's campaign]", the documents said.
"[Mr Page] has established relationships with Russian Government officials, including Russian intelligence officers."
The documents were part of officials' application for a warrant to the secretive foreign intelligence surveillance court, which signed off on surveilling Mr Page and include applications and renewal warrants filed in 2017 after Mr Trump took office.
The documents said Mr Page was believed to be the subject of "targeted recruitment" by the Russian government
Republicans have contended that the FBI made serious missteps when it sought a warrant to monitor Mr Page in October 2016 shortly after he left the Trump campaign.
Last week, a federal grand jury charged 12 Russian intelligence officers with hacking Democratic computer networks in 2016, in the most detailed US accusation yet that Moscow meddled in the presidential election to help Mr Trump.
Earlier this year, 13 other Russians and three Russian companies were indicted on charges of conspiring to interfere with the election.