The Pakistani government blocked access to Twitter over potential "blasphemous" caricatures of the prophet Muhammad, according to several reports.

Twitter was asked by the government to stop a discussion about a contest over Muhammad caricatures, something it refused to do. As a result, access to the site has been blocked, according to the Express Tribune. The Pakistan Telecommunications Authority passed down the directive to Internet service providers in the country, and said it couldn't say how long the site would be blocked.

Access to Twitter in Pakistan was later restored on orders from Prime Minister Yousaf Raza Gilani, according to a report in the Express Tribune.

CNET contacted Twitter for comment. We will update the story when we get a response.

The discussion was about a competition to post images on Facebook. Facebook has agreed to address the concerns about the competition, according to Pakistani blog Dawn.com.

Many Muslims consider any image of Muhammad, whether they are positive or negative, to be blasphemous.

Some governments are wary of Facebook's and Twitter's ability to offer citizens a way of communicating and rallying for change. The sites played a critical role in the toppling of governments such as the one in Egypt, and they remain blocked in countries such as China.

Facebook's site was banned for two weeks in Pakistan two years ago for running a similar contest. The move ignited protests in Pakistan, but Facebook eventually blocked the offending content.

Updated at 11:10 a.m. to indicate service has been restored.