WASHINGTON (REUTERS) - The White House on Sunday (March 5) asked the US Congress to examine whether the Obama administration abused its investigative authority during the 2016 campaign, as part of the ongoing congressional probe into Russia's influence on the election.

The request came a day after President Donald Trump alleged, without supporting evidence, that then-President Obama ordered a wiretap of the phones at Mr Trump's campaign headquarters in Trump Tower in New York.

White House spokesman Sean Spicer said Mr Trump and administration officials would have no further comment on the issue until Congress has completed its probe, potentially heading off attempts to get Mr Trump to explain his accusations.

"Reports concerning potentially politically motivated investigations immediately ahead of the 2016 election are very troubling," Mr Spicer said in a statement.

Mr Trump made the wiretapping accusation in a series of early morning tweets on Saturday amid expanding scrutiny of his campaign's ties to Russia. An Obama spokesman denied the charge, saying it was "a cardinal rule" that no White House official interfered with independent Justice Department investigations.

Under US law, a federal court would have to have found probable cause that the target of the surveillance is an "agent of a foreign power" in order to approve a warrant authorising electronic surveillance of Trump Tower.