US senator Joe Lieberman has been involved in an angry war of words with YouTube and Google over Al-Qaeda videos appearing on the popular video sharing site.

Lieberman initially complained to Google, which owns YouTube, about videos on the site which showed the killing of US troops, along with propaganda videos with an Al-Qaeda logo and messages from other terrorist groups.

The senator demanded that the videos be taken down immediately. "Protecting our citizens from terrorist attacks is a top priority for our government. The private sector can help us do that," he said.

"By taking action to curtail the use of YouTube to disseminate the goals and methods of those who wish to kill innocent civilians, Google will make a singularly important contribution to this important national effort."

YouTube responded by taking down some of the videos which feature violence and hate speeches, thought to number around 80, but has refused to take down others as they do not violate the site's terms and conditions.

"Senator Lieberman stated his belief that all videos mentioning or featuring these groups should be removed from YouTube, even legal non-violent or non-hate speech videos," YouTube said on the company blog.

"While we respect and understand his views, YouTube encourages free speech and defends everyone's right to express unpopular points of view.

"We believe that YouTube is a richer and more relevant platform for users precisely because it hosts a diverse range of views, and rather than stifle debate we allow our users to view all acceptable content and make up their own minds."

However, YouTube's apparent even-handedness was not enough for the senator. "That is a start but it is not enough," he said.

"No matter what their content, videos produced by terrorist organizations like al-Qaeda, that are committed to attacking America and killing Americans, should not be tolerated. Google must reconsider its policy."