President Donald Trump joked Monday about his ties to Russia after a bombshell report said the FBI had opened an investigation into whether he was acting as a Russian agent.

Trump said on Twitter that his policies had resulted in low gas prices and more domestically produced oil, which did not help Russia.

"But this is bad news for Russia, why would President Trump do such a thing? Thought he worked for Kremlin?" he tweeted.

A report from The New York Times on Friday said the FBI began investigating whether Trump was a witting or unwitting Russian agent after he fired FBI Director James Comey in 2017.

President Donald Trump on Monday joked about suspicions over his ties with Russia, following a new report indicating that the FBI had opened an investigation into whether he was an agent of the Russian government.

Trump cited "Fox and Friends" on Twitter on Monday morning in touting a claim that gasoline prices in the US were falling because he had curtailed energy regulations.

He presented this as bad news for Russia and therefore proof that he was not working in its interests.

"But this is bad news for Russia, why would President Trump do such a thing? Thought he worked for Kremlin?" he tweeted.

—Donald J. Trump (@realDonaldTrump) 14 January 2019

A bombshell New York Times report on Friday indicated that Trump's firing of FBI Director James Comey in May 2017 prompted the FBI to open a counterintelligence investigation into whether Trump was intentionally or unintentionally working on behalf of Russia.

The bureau was already investigating whether any members of Trump's presidential campaign colluded with Moscow to meddle in the 2016 election, but Friday's report was the first indication that the FBI thought Trump himself could have been acting, wittingly or unwittingly, as a Russian agent.

Read more: The FBI reportedly started investigating whether Trump was a Russian asset after he fired Comey

The Times said that the special counsel Robert Mueller took over the counterintelligence investigation from the FBI and that it was unclear whether that investigation remained ongoing.

Trump first responded to the report on Saturday, when he tweeted that former FBI leaders were "corrupt" and opened up an investigation with "no reason & with no proof."

He also repeated his now-familiar attacks on Comey, calling him "Lyin' James Comey" and a "total sleaze."