Pakistan telecom authorities have blocked several websites inviting people to draw cartoons of the Prophet Muhammad, it has emerged.
Protests over the cartoons continue in Pakistan
Instructions were issued to internet service providers across Pakistan on 27 February to block about a dozen websites of various origins.
The ban comes amid protests in several Muslim countries against the cartoons, first published in Denmark last year.
Islamic tradition prohibits depictions of the Prophet.
Bloggers in Pakistan first became aware of the ban on 28 February when they were unable to access a popular blog hosting site, Blogspot.
One of the blocked sites is hosted on Blogspot, which led to the blocking of all web journals hosted on the site.
The Pakistan bloggers found their blogs blocked, even though their blogs are not connected with the cartoons.
They say they have still been able to edit and update their blogs, but not able to read them.
Blogspot, which hosts web logs, has been blocked
Many are using anonymizers - a service which allows people to surf sites without being identified - to access their sites, while the US blogging community has sent out suggestions for ways in which Blogspot can be accessed.
The BBC's Aamer Ahmed Khan in Karachi says the blocking is unlikely to turn into a major freedom of expression issue in Pakistan as there seems to be a consensus against allowing such freedom to extend to irreverent treatment of religious figures.
Pakistani bloggers agree the blocking of Blogspot cannot be intentional, but are hoping the authorities realise the problem soon and rectify it, he said.
There are many ways of blocking specific sites without letting it affect the entire hosting facility, bloggers say.
Pakistan, meanwhile, is seeking an internationally applicable law against blasphemy.