The newly revealed exchanges provide additional information about the role played by Trump jnr in 2016. He also has come under scrutiny for agreeing to meet 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 jnr's lawyer, 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. 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 jnr sought to learn more about a rumoured leak of new documents related to Clinton, the messages indicate. "What's behind this Wednesday leak I keep reading about?" Trump jnr asked during one exchange on October 3.
More than a week later, on October 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 jnr 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 jnr 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/."
Yesterday, White House lawyer Ty Cobb declined to comment, referring questions about the exchanges to Trump jnr's lawyer.
Futerfas noted that Trump jnr 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 yesterday that he could not confirm the messages because WikiLeaks does not retain its Twitter messages. But he wrote that Trump jnr 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 yesterday 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 [yesterday]".
Congressman Adam Schiff, 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 jnr's messages "unprecedented".
He added: "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. 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."
Meanwhile, Attorney-General Jeff Sessions is entertaining the idea of appointing a second special counsel to investigate a host of Republican concerns - including alleged wrongdoing by the Clinton Foundation and the controversial sale of a uranium company to Russia - and has directed senior federal prosecutors to explore at least some of the matters and report back to him and his top deputy, according to a letter obtained by the Washington Post.
The revelation came in a response from the Justice Department to an inquiry from House Judiciary Committee Chairman Robert Goodlatte, (R), who in July and again in September called for Sessions to appoint a second special counsel to investigate concerns he had related to the 2016 election and its aftermath.
The list of matters he wanted probed was wide ranging, but included the FBI's handling of the investigation into Hillary Clinton's use of a private email server while she was secretary of state, various dealings of the Clinton Foundation and several matters connected to the purchase of the Canadian mining company Uranium One by Russia's nuclear energy agency.