After blocking Facebook and Youtube, Pakistani authorities today further widened the crackdown on websites with blasphemous contents by restricting access to popular social networking website Twitter.

Pakistani users were unable to log into Twitter after internet service providers blocked access to the site.

When users tried to log into site, there browsers displayed a message that said "this site is restricted."

Over the past two days, Pakistan Telecommunication Authority has blocked websites like Facebook and Youtube, citing "sacrilegious contents" on the websites as the reason for the action.

The crackdown began after the Lahore High Court issued an order for blocking Facebook over a page hosting a contest for blasphemous caricatures of Prophet Mohammad.

Over 450 URLs have been blocked so far by the authorities.

Pakistan Telecommunication Authority (PTA) yesterday said that YouTube had been blocked due to "sacrilegious contents" but did not point to specific material on the website that prompted the authorities to block it.

The government acted against both Facebook and YouTube after it failed to persuade the websites to remove the "derogatory material," the statement said.