The ban, which has proven to be not entirely effective, is the latest effort by a government to squash critical comments that flow freely over Twitter's social network and highlights the thorny policy challenge facing the company.

Analysts and observers said they were not immediately concerned that the ban in Turkey could embolden other governments to follow suit and clamp down on Twitter. But the company's easy-to-use communications service and its long-running support of free speech have made it a visible target for some governments.

While Twitter has earned the ire of other governments, Turkey's move to ban Twitter is particularly noteworthy, said Jillian York, director for international freedom of expression at the Electronic Frontier Foundation.