Guinea's opposition parties pulled their delegates out of the national electoral commission on Thursday after rejecting some provisional results from Sunday's parliamentary election, meant to cap a transition to democracy.
The National Electoral Commission (CENI) began announcing election results on Wednesday, with President Alpha Conde's ruling RPG party taking an early lead in several districts.
But the opposition said it had won the Dubreka district, about 50 km (30 miles) from the capital Conakry.
"We won Dubreka and categorically reject the results announced by the CENI yesterday," said former prime minister Sidya Toure, leader of the opposition UFR party.
He said the opposition was withdrawing its observers from the centre where votes were slowly being tallied, saying their presence was serving no purpose.
"They were not even allowed to speak," Toure said.
The election, over two years overdue and meant to cap Guinea's transition to democracy following a 2008 military coup, was preceded by months of political manoeuvring and protests over the preparations.
At least 50 people were killed in political violence and the climate of instability deterred investment in the world's largest bauxite exporter.
The opposition, which had accused Conde's government of trying to rig the outcome in the run up to the poll, had warned it would not tolerate any attempt to steal the ballot.
No party is expected to win an outright majority in the 114-seat parliament, and parties are expected to try to form coalitions after the results are known.
A spokesman for Conde's RPG party dismissed the opposition complaints.
"The process is taking place in the presence of foreign election observers to guarantee transparency. If the opposition does not agree with the results, there are legal means to complain, notably the Supreme Court," Moustapha Naite said.