Opposition calls for a voter boycott in the Republic of Congo’s presidential election appeared to be cutting into the turnout Sunday, but it was unclear how this would affect longtime President Denis Sassou-Nguesso’s bid for another term.

Sassou-Nguesso, who has been in power in the small, oil-rich nation intermittently since 1979, faces 12 opponents. But six of them — including main challenger Mathias Dzon — called for voters to stay home after allegations of fictitious voter registration lists.

Election administrator Raymond Mboulou said he had witnessed no problems in the capital and that the boycott portended well for the president. Other election officials in the capital said they had witnessed no problems at polling stations on Sunday.

The African Union sent 170 observers. The European Union and several human rights groups have previously expressed concern about possible election irregularities.

Opposition supporters south of the capital told The Associated Press that thugs had taken away their ballot boxes on Sunday.

“They are confiscating ballot boxes in certain villages along the railway between Kinkala and Mindouli,” said witness Didier Boutsindi.

Mboulou said the government hoped to announce the election results by Thursday.

Election officials and government officials declined to make predictions about the results before voting wrapped up at 6 p.m. Sunday. (1700 GMT, noon EDT)

But ruling party supporters said they were certain the president had secured victory because of the boycott.

“The victory is acquired, but we’re worried about the rate of abstention,” said supporter Mathias Djendza, who said he was concerned that a flood of opposition voters would decide to vote at the last minute.

But opposition voters appeared to heed the boycott. At one location in southern Brazzaville, where opposition members have more support, as few as 52 of 924 registered voters showed up to vote

In Sassou-Nguesso’s strongholds in the northern parts of the capital city, observers said voters turned out in large numbers to support the president. In the town of Makoua, another support base some 360 miles (600 kilometers) north of the capital, voters thronged the polls, witnesses said.

Sassou-Nguesso claimed power in 1979 after a coup and ruled until a 1992 election defeat. He seized power again in 1997 with help from Angolan troops. In 2002, he rewrote the constitution to give more power to the presidency and was re-elected.

Another victory would vault Sassou-Nguesso into an elite group of three-decade rulers in Africa. Other long-standing rulers include Angola’s Jose Eduardo dos Santos, Equatorial Guinea’s Teodoro Obiang, who both took power in 1979, and Zimbabwe’s Robert Mugabe, who has ruled since 1980.

In May, a French judge called for an investigation into Sassou-Nguesso and two other African leaders on charges of money laundering and other alleged crimes linked to their wealth in France.

The probe follows a complaint by Transparency International France, an association that tracks corruption, against Sassou-Nguesso and Obiang of Equatorial Guinea. Gabon’s Omar Bongo was also named in the probe but he has since died.

Copyright 2009 The Associated Press.