MTN Cameroon, one of the country's three cell service providers, shut down access to the micro-blogging site after receiving a request from the government, the Committee to Protect Journalists' Mohamed Keita wrote on the organisation's web site, citing a Tweet by an MTN marketing manager.
"For security reasons, the government of Cameroon requests the suspension of the Twitter SMS integration on the network," the marketing manager, Bouba Kaele, reportedly wrote in the Tweet, which was later deleted.
A subscriber to MTN Cameroon's mobile Twitter service told AFP the company had sent clients a message announcing the suspension, citing "reasons beyond (its) control."
The shut-down comes as President Paul Biya, in power since 1982, confronts calls for an uprising against him circulated via Internet and text messages over the past several weeks.
Government spokesman Issa Tchiroma, who is also the communication minister, told AFP he did not have "perfect knowledge of the situation" surrounding MTN's Twitter suspension.
But, he added, "I remind you of one thing: it is the government's responsibility to protect the nation."
South Africa-based MTN launched its mobile Twitter service in Cameroon in November. Some 50 subscribers used the service, according to local blogs and web sites. Twitter is still accessible in Cameroon via Internet.
The government has grown increasingly wary of the role Twitter and other social networks could play in sparking an Egypt- or Tunisia-style uprising, said the director of a local non-government organisation, speaking on condition of anonymity.
"The Cameroonian government dreads more and more the use of social networks to issue calls for resistance" against Biya's regime, she told AFP, adding that authorities have already issued warnings to MTN Cameroon and Orange-Cameroon, another provider.
Tchiroma said the communication and post and telecommunications ministries had called telecom companies to a meeting last week for a "dialogue with communicators," and planned to hold similar meetings with the country's bloggers, web site editors and TV and radio broadcasters.