The Committee to Protect Journalists (CPJ) says the government of the Republic of Congo should lift the total communication blackout it imposed before the 20 March presidential elections.
On 19 March Congolese interior minister Raymond Mboulou ordered telecommunication companies to cut all mobile phones, text message and internet services for at least 48 hours in order to prevent "illegal" transmission of election results.
However, the blackout remains in effect.
CPJ said it called the president of the High Council of Freedom of Communication to demand the lifting of the blackout, but that the call went unanswered.
The Embassy of the Republic of Congo in Washington also failed to respond to requests for comment by e-mail and phone, according to CPJ.
CPJ deputy executive director Robert Mahoney said plunging a country into a communication Dark Age on unfounded fears is reckless. "Democracy does not work without a free press. We call on the government to restore all communications immediately and ensure that journalists can do their job. Failure to do so undermines confidence in the entire election process," Mahoney said.
Republic of Congo President Denis Sassou Nguesso is among the longest serving presidents in Africa. He is widely expected to be announced the winner of the elections.
Congo is the latest country in Africa to ban the use of social media during elections.
In Uganda, during its recent elections, the government banned social media in a bid to prevent citizens from transmitting election results.
Ugandan president Yoweri Museveni defended the ban as a "security measure to avert lies intended to incite violence and illegal declaration of election results.