BRAZZAVILLE, Republic of Congo (AP) — Republic of Congo has instructed telecommunications firms operating in the country to block service during Sunday's presidential vote, citing security reasons.

All communications including text messages should be blocked on Sunday and Monday, according to a letter dated Friday from Raymond Zephirin Mboulou, the interior minister, to the head of local operations for the South African-based firm MTN.

The letter, obtained by The Associated Press on Saturday, refers to a list of numbers that are to continue to receive communications during the two days.

Republic of Congo's longtime President Denis Sassou N'Guesso is facing off against eight opponents Sunday in a presidential contest held five months after a referendum removed term and age limits that would have barred him from running.

The run-up to October's referendum was marred by violence, with security forces cracking down on anti-referendum demonstrators. The official death toll was three, though critics of Sassou N'Guesso say the number of demonstrators killed was likely higher.

Residents of the capital, Brazzaville, said this week they were worried about insecurity during the vote. "All conditions are currently met for political violence in Brazzaville," said Marcelle Foundou, who lives in the city's southern Bacongo neighborhood but has temporarily relocated to a northern neighborhood believed to be safer.