Pakistan will begin screening seven well-known websites for blasphemous material, including Google, Yahoo and online bookseller Amazon, an official has said.
Seventeen smaller websites with anti-Islamic messages will be blocked completely for users in the country in response to a recent court order governing what content should be available on the internet.
Khurram Mehran, a spokesman for Pakistan's telecommunication authority, said that Yahoo, Google, MSN, Hotmail, YouTube, Amazon and Bing will be screened for sacriligious content, which he said would be blocked to prevent users from accessing it.
"If any particular link with offensive content appears on these websites, the (link) shall be blocked immediately without disturbing the main website," Mehran said.
Pakistan controversially banned the social networking site Facebook in May after it hosted a page encouraging users to post images of the Prophet Muhammed. Many Muslims regard any image of prophet as blasphemous. YouTube was also blocked for a short time.
The Facebook page sparked protest in Pakistan, but the decision of authorities to ban the website also caused controversy, with many questioning why people were not allowed to make up their own minds whether or not to look at the images.
Facebook eventually blocked the page and the ban on the site was lifted, but not before critics said that Pakistan had gone further than more conservative Islamic countries in blocking access to the social networking site.
Mehran said that the telecommunications authority had been instructed by the ministry of information technology to begin the process of blocking and monitoring the various sites immediately.