Germany's defence minister has denied newspaper allegations that he committed plagiarism in his PhD thesis.
Karl-Theodor zu Guttenberg got top marks for his 2006 law dissertation from the University of Bayreuth.
But the Suddeutsche Zeitung says several long passages in the thesis seem to have just been lifted from other people's work.
The minister, who is currently on a visit to Afghanistan, has dismissed the accusations as "absurd".
The popular 39-year-old has been a lawmaker in Chancellor Angela Merkel's conservative bloc since 2002 and is considered a possible future candidate for the top post.
His thesis - titled Constitution and Constitutional Treaty: Constitutional Developments in the US and EU - was completed in 2006.
'Word for word'
The Suddeutsche Zeitung claims Mr zu Guttenberg copied, word for word, one passage from a newspaper article and another from a public lecture, without attributing them, while other texts were incorrectly attributed.
Professor Barbara Zehnpfennig, whose newspaper article was allegedly used in the opening of the dissertation, told German news channel N24 that failing to credit another author "breaks all academic rules".
Spiegel magazine reported that the minister had also used a paragraph from the US Embassy website without attribution.
While vehemently rejecting the accusations of plagiarism, the minister told reporters he was happy to check to see whether there had been any omissions or errors in the 1,200 footnotes.
The paper suggests he was under stress to finish his dissertation while working as a member of parliament.
"Should someone come up with the idea that a member of my office may have collaborated on the academic preparation of my dissertation, I would have to answer - it's simply not true," said Mr Guttenberg. "The writing of the dissertation was my own work."
The university said it would investigate the allegations.
Mrs Merkel's spokesman said the chancellor was taking an interest in the case but would wait for a decision from university authorities before passing judgement.
'Credibility at stake'
The BBC's Stephen Evans in Berlin says the defence minister is feeling the political heat at the moment.
He has been criticised over a scandal on a military training ship which led to a mutiny - bringing the charge from opponents that his defence ministry is out of control.
On top of that, says our correspondent, a soldier shot in Afghanistan was initially said by the ministry to have shot himself, but turned out to have been shot by another soldier.
The latest controversy surrounding Germany's charismatic defence minister emerged when a Bremen University law professor began writing a review of the dissertation which was published two years ago, with the aid of internet search engines.
Rainer Arnold, defence expert with the opposition Social Democrats (SPD), told German media that if the accusations of plagiarism were found to be true, then Mr zu Guttenberg would lose all credibility "and a minister who's lost his credibility can't really work any more".
Germany news agency DPA reported that the defence minister was visiting the Baghlan province in northern Afghanistan on Thursday and had spent the night with German forces in one of the most dangerous areas in which they were operating.