The Republic of Congo's government has ordered telecom providers to block all service during Sunday's presidential election.
Congo Interior Minister Raymond Zephirin Mboulou sent a letter to the country's two main telecom firms, saying that for reasons of national security, they were to block all communication, including text messages, on Sunday and Monday.
The letter, copies of which have appeared online, also referred to a list of numbers that will continue to receive communication during the vote.
The order could raise tensions in the country, where longtime President Denis Sassou Nguesso is running for re-election against eight opponents, including former General Jean-Marie Mokoko.
Mokoko, who is seen as the president's strongest challenger, was summoned to report to police headquarters on Saturday for unspecified reasons.
Sassou Nguesso, 71, has ruled Congo for 32 of the last 37 years. Last October, he pushed through a constitutional change that eliminated a two-term limit and an age limit of 70 for presidential candidates.
The opposition boycotted the referendum in which the change was approved and said turnout percentage for that vote was in the single digits.