Opposition leader Agbeyome Kodjo says authorities used ballot stuffing, fake polling stations and people casting multiple votes to skew results in President Faure Gnassingbe's favour.
Togo tallied ballots on Sunday after a key challenger insisted he could cause a shock upset despite what he claimed was "fraud" in an election President Faure Gnassingbe was widely expected to win.
Troops briefly surrounded the homes of opposition candidate Agbeyome Kodjo and one of his main allies shortly after voting ended on Saturday in a move the authorities said was for their "own safety".
"I have the conviction that in the coming week, I will lead this country," Kodjo told journalists at a press conference in his house after the security forces left.
"Considering the revelations of fraud which marked this ballot, it is impossible for the outgoing candidate to be elected in the first round."
Kodjo claimed the authorities had used ballot stuffing, fake polling stations and people casting multiple votes to skew the results in the incumbent's favour.
Kodjo has emerged as a dark house challenger looking to stop Gnassingbe's bid for a fourth term in office that would extend his family's half-century domination over the West African nation.
The president and his supporters had been confident of a resounding victory in the first round, despite widespread disillusionment after 53 years of dynastic rule that has failed to drag many out of poverty.
The challenger said figures gathered from various polling stations showed he was in the lead in the capital Lome and the coastal region and had "good scores" in other areas.
The election commission is expected to release the official provisional results early next week.
The situation around Lome was calm on Sunday morning, an AFP news agency journalist reported.
Internet connections appeared to be sporadically interrupted.
Gnassingbe has led the West African country of eight million people since taking over in 2005 following the death of his father Gnassingbe Eyadema, who ruled with an iron fist for 38 years.
Kodjo, a former prime minister under Gnassingbe's father, gained ground during the campaign after winning the backing of an influential former Catholic archbishop.
The authorities banned hundreds of local observers from monitoring the election and cancelled the system of electronic security at the last moment.
Some 300 international observers were deployed, mainly from the Economic Community of West African States (ECOWAS) and the African Union, with many African states supporting the incumbent.
The six opposition challengers have suggested they will unite against the president if he fails to win an outright majority and the election goes to a second round.
That vote would be held 15 days after the announcement of the final results.
Stability and security
The authorities faced major protests in 2017 and 2018 demanding an end to the Gnassingbe family's five-decade stranglehold.
But the demonstrations petered out in the face of government repression and squabbles among the opposition.
Last May, Gnassingbe oversaw an overhaul of the constitution that allowed him to run this year and potentially remain in office until 2030.
Despite economic growth of around five percent, around half of Togo lives on less than $1.90 per day.
Stability and security are central to Gnassingbe's message as militant violence rocks its northern neighbour Burkina Faso.
Togo has so far managed to prevent the bloodshed spilling over and its army and intelligence service are among the most effective in the region.