An online video has emerged purporting to show Syria's deputy oil minister defecting and joining the opposition against President Bashar Assad.

In the video posted on YouTube on Thursday, a man wearing a suit and tie identifies himself as Abdo Husameddine and says he is Syria's deputy oil minister.

Reading from a paper, he says he is defecting because of Assad's brutal crackdown that has killed thousands of people in the past year.

If confirmed, this would be the highest ranking official in Assad's administration to defect since the uprising began a year ago. There have been scores of army defections but civilian government officials have remained largely loyal to Assad's regime.

It was not clear when or where the video was filmed. There was no immediate comment from Damascus.