Officials in Pakistan say the government will begin monitoring major websites, including Google and Yahoo, for material it deems offensive to Islam.
The Pakistan Telecommunications Authority also said it will block 17 lesser-known sites for containing blasphemous content, in response to a court order.
Among the websites that will be monitored are Amazon, MSN, Hotmail and Bing.
Friday's move follows the temporary blocking last month of the social networking site Facebook, after someone using the site sought to collect images of the Prophet Muhammad. The Pakistani government also temporarily banned the video website YouTube for distributing allegedly sacrilegious or profane material.
In recent years, Western newspapers' publication of caricatures of the prophet have triggered violent protests in majority-Muslim countries including Pakistan. Islam forbids any depiction of the prophet.
Some information for this report was provided by AP and AFP.
