The popular video hosting website YouTube said on Monday it had mistakenly shut down two accounts of the Syrian Observatory for Human Rights, a key source of information in the 21-month Syria conflict.

"With the massive volume of videos on our site, sometimes we make mistakes. When an error is brought to our attention we act quickly to reinstate the videos in question," a YouTube spokesperson told AFP on condition of anonymity.

YouTube sent the Observatory an email on Sunday that said its channels "syrianhro" and "almrsd" had "violated the policy of the site by publishing shocking and offensive videos," the Britain-based watchdog said.