Washington, Sep 25 (IANS): US President Barack Obama reportedly used a pseudonym in some of the e-mails he exchanged with Hillary Clinton when she served as his Secretary of State from 2009-2013, according to new documents released by the FBI.

The FBI on Friday released its second batch of documents -- comprising 189 pages -- from its two-year investigation into Clinton's use of a private e-mail server during her time as Secretary of State, EFE news reported.

The documents include FBI interviews with some of Clinton's top aides such as Huma Abedin, who in an interview conducted on April 5, 2016, was shown e-mail correspondence between Clinton and another person, although Abedin said she did not recognise that other person's identifying designation, the online news Web site Politico reported.

"Once informed that the sender's name is believed to be (a) pseudonym used by the President, Abedin exclaimed: 'How is this not classified?'" the report stated. "Abedin then expressed her amazement at the President's use of a pseudonym and asked if she could have a copy of the e-mail."

Congressional Republicans, just six weeks before the November 8 election, continue to press the FBI to make public more material from their investigation, which ended in July with Director James Comey concluding that no charges could be filed against Clinton despite the fact that she had been "extremely careless" in handling certain classified information.

The Clinton campaign, in a communique from spokesman Brian Fallon, said that the new documents published on Friday show why the Department of Justice believes that there is no basis for pursuing the case.