President Donald Trump's eldest son exchanged private messages with WikiLeaks during the presidential campaign at the same time the website was publishing hacked emails from Democratic officials, according to correspondence made public Monday.

Donald Trump Jr. did not respond to many of the notes, which were sent using the direct message feature on Twitter. But he alerted senior advisers on his father's campaign, including his brother-in-law, Jared Kushner, according to two people familiar with the exchanges.

In the messages, WikiLeaks urged Trump Jr. to promote its trove of hacked Democratic emails and suggested that President Trump challenge the election results if he did not win, among other ideas. They were first reported by the Atlantic and later posted by Trump Jr. on Twitter.

WikiLeaks, which bills itself as an anti-secrecy group, was described in April by CIA Director Mike Pompeo as a "non-state hostile intelligence service often abetted by state actors like Russia."

In July 2016, the organization released thousands of emails that had been stolen from the Democratic National Committee by a cyberhack that U.S. intelligence officials concluded was orchestrated by the Russian government.

The newly revealed exchanges provide additional information about the role played by Trump Jr. in 2016. He also has come under scrutiny for agreeing to meet with a Russian lawyer in Trump Tower who he was told wanted to provide "dirt" about Democratic nominee Hillary Clinton on behalf of the Russian government.

Alan Futerfas, Trump Jr.'s attorney, said his client's exchanges with WikiLeaks were innocuous.

"All sides in this campaign, the Clinton side, the Trump side, were monitoring WikiLeaks to see what they would publish next," Futerfas said. "If The Washington Post or the New York Times was looking to see what was being released, does that suggest any impropriety on their part? Of course not."

At one point during his communication with WikiLeaks, Trump Jr. sought to learn more about a rumored leak of new documents related to Clinton, the messages indicate.

"What's behind this Wednesday leak I keep reading about?" Trump Jr. asked during one exchange with the WikiLeaks account on Oct. 3.

More than a week later, on Oct. 12, the account replied with a suggestion:

"Hey Donald, great to see you and your dad talking about our publications," WikiLeaks wrote. "Strongly suggest your dad tweets this link if he mentions us." The message included a link to search documents that had been hacked from Clinton campaign chairman John Podesta.

Trump Jr. did not answer. Fifteen minutes later, his father tweeted to his millions of followers: "Very little pick-up by the dishonest media of incredible information provided by WikiLeaks. So dishonest! Rigged system!"

Two days later, Trump Jr. tweeted the link to his followers, writing, "For those who have the time to read about all the corruption and hypocrisy all the @wikileaks emails are right here: http://wlsearch.tk/."

On Monday, White House lawyer Ty Cobb declined to comment, referring questions about the exchanges to Trump Jr.'s lawyer.

Futerfas noted that Trump Jr. ignored several of WikiLeaks' suggestions, including that he leak his father's tax returns to the group.

"Their attempts to get information were unsuccessful, and he did not bite," he said.

Julian Assange tweeted Monday that he could not confirm the messages because WikiLeaks does not retain its Twitter messages. But he wrote that Trump Jr. was "rebuffed" when he asked for information, comparing him to "thousands" of others who had also asked and been similarly ignored.

During the campaign, Vice President Mike Pence said the Trump team had nothing to do with WikiLeaks. "Nothing could be further from the truth," Pence told Fox News on October 12 when asked if the campaign was "in cahoots" with the group.

Alyssa Farah, a Pence spokesman, said Monday that he was "never aware of anyone associated with the campaign being in contact with WikiLeaks."

"He first learned of this news from a published report earlier [Monday]," she said.

On Monday, Rep. Adam Schiff, Calif., the top Democrat on the House Intelligence Committee, said the messages were "yet another secret communication between the Trump campaign and cut-outs for the Kremlin."

Clinton Watts, a former FBI agent who has been tracking the Russian influence effort, called Trump Jr.'s messages "unprecedented."

"I can't think of any time in history where a foreign government, through a cut-out has been able to tap directly into a campaign in this way," he said. "It shows they were complicit to this and how amenable they were to hurting another American, even if the source came from a foreign government."

The Washington Post's Karoun Demirjian, Tom Hamburger, Ellen Nakashima and Julie Tate contributed to this report.