Pakistan blocked Twitter on Sunday because of messages they say are offensive to Islam.

The tweets were promoting a competition on Facebook to post images of Islam's Prophet Muhammad, Mohammad Yaseen, chairman of the Pakistan Telecommunication's Authority told Reuters news agency.

Two years ago, Facebook was als obanned by Pakistan authorities for a similar reason. That ban lasted for around a fortnight until Facebook blocked access to the controversial page in Pakistan.

Now, Twitter seems to have refused blocking the specific tweets. The response from Pakistan's Ministry of Information Technology was to block the popular social network in the country.

The Internet Service Providers Association of Pakistan told Reuters its members had been asked to block Twitter indefinitely but the government had not given them a reason.

US-based Human Rights Watch called the ban "ill-advised, counterproductive and futile".