The moves follow a temporary ban imposed on Facebook in May that drew both praise and condemnation in a country that has long struggled to figure out how strict a version of Islam it should follow.
Both the Facebook ban and the move announced Friday were in response to court orders. The sites to be monitored include Yahoo, Google, MSN, Hotmail, YouTube, Amazon and Bing, said Pakistan Telecommunication Authority spokesman Khurram Mehran.
"If any particular link with offensive content appears on these websites, the (link) shall be blocked immediately without disturbing the main website," Mehran said.
An example of one of the 17 sites being blocked include islamexposed.blogspot.com, Mehran said. That site features postings with headlines such as "Islam: The Ultimate Hypocrisy" and links to anti-Islam online petitions.
Mehran said that, under instructions from the Ministry of Information Technology, the authority had begun the process of barring and monitoring the various sites.
Facebook was not part of the latest petition ruled upon by the judge in the city of Bahawalpur, Mehran said.
It was not possible late Friday to obtain a copy of the judge's order. Attempts to get comments from the affected companies also were not immediately successful.
A top court ordered the ban on Facebook for about two weeks in May amid anger over a page that encouraged users to post images of Islam's Prophet Muhammad. Many Muslims regard depictions of the prophet, even favorable ones, as blasphemous. YouTube also was briefly blocked at the time.
The Facebook ban was lifted after the social-networking company blocked that particular page in Pakistan, but officials said at the time that the government would keep blocking some other, unspecified sites that contain "sacrilegious material." The Facebook controversy sparked a handful of protests across Pakistan, many by student members of radical Islamic groups. Some of the protesters carried signs advocating holy war against the website for allowing the page.
It also sparked a good deal of soul-searching, especially among commentators, who questioned why Pakistanis could not be entrusted to decide for themselves whether or not to look at a website.
Some observers noted that Pakistan had gone further than several other Muslim countries by issuing a ban on Facebook, and said it underscored the rise of conservative Islam in a South Asian nation once more influenced by moderate Sufi traditions.
It was not the first time that images of the prophet have sparked anger.
Pakistan and other Muslim countries saw large and sometimes violent protests in 2006 after a Danish newspaper published cartoons of Muhammad, and again in 2008 when they were reprinted. Later the same year, a suspected Al-Qaeda suicide bomber attacked the Danish Embassy in Islamabad, killing six people.
