In this Friday, Feb. 10, 2017, photo, President Donald Trump waves to supporters on the steps of Air Force One

US President Donald Trump on Saturday accused former president Barack Obama of wire tapping him in October during the late stages of the presidential election campaign, but offered no evidence to support the allegation.

“How low has President Obama gone to tapp my phones during the very sacred election process. This is Nixon/Watergate. Bad (or sick) guy!,” Trump said in a series of Tweets on his Twitter account early on Saturday.

In one of the tweets, Trump said the alleged wire tapping took place in his Trump Tower, but there was “nothing found”.

Trump’s administration has come under pressure from FBI and congressional investigations into contacts between some members of his campaign team and Russian officials during his campaign.

Obama imposed sanctions on Russia and ordered Russian diplomats to leave the US in December over the country’s involvement in hacking political groups in the Nov. 8 US presidential election.

Trump’s national security adviser, Michael Flynn, resigned in February after revelations that he had discussed US sanctions on Russia with the Russian ambassador to the United States before Trump took office.

Flynn had promised Vice President Mike Pence he had not discussed US sanctions with the Russians, but transcripts of intercepted communications, described by US officials, showed that the subject had come up in conversations between him and the Russian ambassador.

Trump has often used his Twitter account to attack rivals and for years led a campaign alleging that Obama was not born in the US He later retracted the allegation.

Related articles across the web

• Pence: Trump 'will be the best friend' that US governors ever had
• In Europe, Pence says U.S. will hold Russia accountable
• Mike Pence Arrived At Super Bowl, Media Tried To Hide What Happened Next
• Pence used a private email account to conduct state business
• Pence says conservatives have a rare opportunity
• Gov. Baker attending National Governors Association meeting
• WATCH: Donald Trump loves saying "Donald Trump"
• Watch Live: President Trump Speaks at Conservative Political Action Conference
• Mike Pence Will Be Speaking At Notre Dame's Commencement
• Donald Trump pancakes on sale at Moscow pancake festival