German Defence Minister Ursula von der Leyen has denied claims she plagiarised parts of her doctoral thesis.

The crowd-sourced plagiarism hunting website VroniPlag Wiki claims to have found "elements of plagiarism" on 27 of the 62 pages of Ms von der Leyen's 1990 dissertation.

The politician said she had asked her university to have her thesis evaluated after she learned of the allegations.

Two previous cabinet ministers have stepped down after plagiarism scandals.

Ms von der Leyen told German media that it was "not new, that internet activists seek to spread doubts on the dissertations of politicians".

She found out in August that her doctoral thesis was under scrutiny after a tip-off, she told Westfalenpost (in German), and on the same day contacted Hanover Medical School. She has asked them to have an "expert and neutral" commission examine her dissertation, she said.

Ms von der Leyen, of Chancellor Angela Merkel's centre-right CDU party, qualified as a doctor in 1987 and was awarded a doctorate in medicine in 1991, according to her website.

She worked as a gynaecologist and in public health, and had seven children, before entering politics - initially in the state assembly in Lower Saxony.

Ms von der Leyen became a federal cabinet minister in Mrs Merkel's first government, in 2005, and has been defence minister since 2013.

Mrs Merkel has already lost two cabinet ministers after their respective universities withdrew their doctoral titles following plagiarism claims.

In 2011, then-Defence Minister Karl-Theodor zu Guttenberg resigned after he was found to have copied large parts of his thesis.

And in 2013, Education Minister Annette Schavan was forced to step down after her alma mater withdrew her degree.

But it is not just conservative German politicians who have fallen victims to plagiarism allegations - Silvana Koch-Mehrin from the liberal FDP resigned as vice-president of the European Parliament in 2011 after claims that she did not properly source her university thesis. Her university subsequently stripped her of her doctoral title.