San Francisco, Aug 27 (DPA) Online collaborative encyclopedia Wikipedia announced a tightening of its editing rules Wednesday aimed at preventing vandalism, as it becomes an increasingly important source of information.

The new guidelines will require that all edits to articles about living people be approved by authorised editors. The rules represent the most far-reaching changes ever undertaken by the user-written encyclopedia, which had previously allowed anyone to contribute articles or revise information on existing articles.

Founded in 2001, Wikipedia currently boasts more than 13 million articles, including three million in English, and is one of the top 10 sites on the web. But because of its open source nature it is often not considered an authoritative source, and has been hit by numerous high profile cases of vandalism.

The changes, called 'flagged revisions', apply to the English version of the site and were announced Wednesday on the Wikipedia blog.

Under the new policy, articles edited by new contributors will be reviewed by regular contributors, whose comments on the revisions will be posted with the article.