The human rights activist and Nobel Peace Prize laureate Tawakkol Karman has launched a scathing attack on the head of the Syrian regime, describing him as a big criminal and likening him to German Nazi leader Adolf Hitler.

"In Syria, there is a big criminal, who resembles nothing so much as Hitler," said Karman in a statement on her official Facebook page.

She pointed out that al-Assad has so far killed more than half a million people, adding that this brings curse and dishonor on humanity."

"This is the truth you escape by licking your wounds and resorting to fighting against terrorism that you have made in Afghanistan’s mountains," she concluded addressing western governments.