NEW YORK — Most of the world's Internet users lost access to YouTube for several hours Sunday after an attempt by Pakistan's government to block access domestically affected other countries.

NEW YORK — Most of the world's Internet users lost access to YouTube for several hours Sunday after an attempt by Pakistan's government to block access domestically affected other countries.

The outage highlighted yet another of the Internet's vulnerabilities, coming less than a month after broken fiber-optic cables in the Mediterranean took Egypt off line and caused communications problems from the Middle East to India.

An Internet expert likened the cause of the outage to "identity theft" by a Pakistani telecommunications company, which accidentally started advertising itself as the fastest route to YouTube. But instead of serving up videos of skateboarding dogs, it sent the traffic into oblivion.

On Friday, the Pakistan Telecommunication Authority ordered 70 Internet service providers to block access to YouTube.com because of anti-Islamic movies on the site, which is owned by Google Inc.