President Donald Trump said on Sunday he would ask the Justice Department to look into whether his 2016 presidential campaign was infiltrated or surveilled.

"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!" 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

His comment comes after House Intelligence Chairman Devin Nunes said Sunday that U.S. spy agencies crossed a “red line” if they planted a paid informant inside Trump’s campaign.

In an interview on Fox News Channel, Nunes said he and Republican colleagues have yet to determine whether there was such an informant, because the Justice Department and FBI continue to withhold documents from them.

But the California lawmaker pointed to what he said were “leaks” behind news reports in recent days that the Federal Bureau of Investigation had used an “informant” to get information regarding the Trump campaign early in its counterintelligence investigation of possible ties to Russia.

“You can’t do this to political campaigns,” Nunes said.

Deputy Attorney General Rod Rosenstein responded later in the day.

"If anyone did infiltrate or surveil participants in a presidential campaign for inappropriate purposes, we need to know about it and take appropriate action," rosenstein said.

In an earlier tweetstorm Sunday morning, Trump demanded an end to special counsel Robert Mueller's probe into election interference.

It was the president’s first response to a New York Times report on Saturday that an emissary from Saudi Arabia and the United Arab Emirates met with members of Trump’s team, including his eldest son, at Trump Tower in New York about three months before the election, offering to help the billionaire developer win.

He slammed the “failing and crooked” New York Times for a “long & boring story indicating that the World’s most expensive Witch Hunt has found nothing on Russia & me so now they are looking at the rest of the World!”

He then blasted Mueller’s team and called for an investigation into former Secretary of State Hillary Clinton.

"At what point does this soon to be $20,000,000 Witch Hunt, composed of 13 Angry and Heavily Conflicted Democrats and two people who have worked for Obama for 8 years, STOP!" Trump tweeted.

"Republicans and real Americans should start getting tough on this Scam," he added, referring to Clinton.

Finally, he tweeted that because Mueller's probe has "given up on Russia and is looking at the rest of the World" it will continue during the 2018 midterms, "where they can put some hurt on the Republican Party."

Things are really getting ridiculous. The Failing and Crooked (but not as Crooked as Hillary Clinton) @nytimes has done a long & boring story indicating that the World’s most expensive Witch Hunt has found nothing on Russia & me so now they are looking at the rest of the World! — Donald J. Trump (@realDonaldTrump) May 20, 2018

....At what point does this soon to be $20,000,000 Witch Hunt, composed of 13 Angry and Heavily Conflicted Democrats and two people who have worked for Obama for 8 years, STOP! They have found no Collussion with Russia, No Obstruction, but they aren’t looking at the corruption... — Donald J. Trump (@realDonaldTrump) May 20, 2018

...in the Hillary Clinton Campaign where she deleted 33,000 Emails, got $145,000,000 while Secretary of State, paid McCabes wife $700,000 (and got off the FBI hook along with Terry M) and so much more. Republicans and real Americans should start getting tough on this Scam. — Donald J. Trump (@realDonaldTrump) May 20, 2018

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. Don’t worry about Dems FISA Abuse, missing Emails or Fraudulent Dossier! — Donald J. Trump (@realDonaldTrump) May 20, 2018

What ever happened to the Server, at the center of so much Corruption, that the Democratic National Committee REFUSED to hand over to the hard charging (except in the case of Democrats) FBI? They broke into homes & offices early in the morning, but were afraid to take the Server? — Donald J. Trump (@realDonaldTrump) May 20, 2018

....and why hasn’t the Podesta brother been charged and arrested, like others, after being forced to close down his very large and successful firm? Is it because he is a VERY well connected Democrat working in the Swamp of Washington, D.C.? — Donald J. Trump (@realDonaldTrump) May 20, 2018

It’s illegal for foreign governments or individuals to be involved in U.S. elections. But the Senate Intelligence Committee’s top Democrat said the Times report suggested Trump’s campaign had been “clearly receptive” to such offers.

“I don’t understand what the president doesn’t get about the law, that says if you have a foreign nation interfere in an American election, that’s illegal,” Senator Mark Warner of Virginia said on CNN’s “State of the Union.”

An attorney for Donald Trump Jr. confirmed on Saturday that a meeting took place with, among other people, Erik Prince, founder of the private military company Blackwater USA, which is now known as Academi.

“Prior to the 2016 election, Donald Trump Jr. recalls a meeting with Eric (sic) Prince, George Nader, and another individual who may be Joel Zamel. They pitched Mr. Trump Jr. on a social media platform or marketing strategy. He was not interested and that was the end of it,” attorney Alan Futerfas said in an emailed statement.

Zamel, an Israeli social-media expert, has become a focus of Special Counsel Robert Mueller’s investigation into Russian interference in the 2016 campaign, according to media reports. Nader is an emissary for the princes of Saudi Arabia and the UAE. The New York Times reported that Prince, the brother of U.S. Education Secretary Betsy Devos, arranged the meeting.

“If these facts are accurate, it demonstrates yet again just how not only willing but eager the president’s son and the Trump campaign were to solicit to receive foreign help,” Representative Adam Schiff, Democrat of California, said on NBC’s “Meet the Press.”

The specifics of the meeting were previously unknown to the House Intelligence Committee, said Schiff, the panel’s top Democrat.

On Saturday, Trump called on the Justice Department to release documents in light of reports of an FBI informant infiltrating his 2016 campaign, saying on Twitter that the data "can give the conclusive answers."

"If the FBI or DOJ was infiltrating a campaign for the benefit of another campaign, that is a really big deal," Trump said in his post. "Drain the Swamp!"

If the FBI or DOJ was infiltrating a campaign for the benefit of another campaign, that is a really big deal. Only the release or review of documents that the House Intelligence Committee (also, Senate Judiciary) is asking for can give the conclusive answers. Drain the Swamp! — Donald J. Trump (@realDonaldTrump) May 19, 2018

The New York Times and The Washington Post reported Friday that the FBI informant, whom both news organizations did not identify by name, met with several Trump campaign aides during the election after the agency learned that they had suspicious contacts with Russia.

The informant met with Trump campaign aides George Papadopoulos, Carter Page — as well as co-chairman Sam Clovis.

Trump has continued to slam the Russia probe as a "witch hunt" and has demanded that the Justice Department release documents on the informant.

Trump’s attorney, former New York Mayor Rudy Giuliani, is now looking to combine the prospect of the president sitting down for an interview with Mueller with knowing whether the alleged informant had any “incriminating information” on Trump associates.

“What we intend to do is premise it on, ‘If you want an interview, we need an answer to this,’ ” Giuliani said in an interview with the Wall Street Journal published on Sunday.

Also this week, Giuliani said Mueller has indicated that he’s willing to narrow the scope of an interview with the president. That would include foregoing questions about payments by Trump’s personal lawyer to adult film star Stephanie Clifford.

Material from Reuters and Bloomberg news services was used in this story.