Liberia's opposition parties say they will participate in a second-round presidential vote, despite rejecting the first-round results.

Second-place candidate Winston Tubman and other members of the opposition said Sunday they will call off a boycott since the preliminary results show no candidate has won the outright majority needed to avoid a run-off.

But they cautioned the National Election Commission to be careful to avoid any fraud in the next round of voting, scheduled for November 8.

According to the most recent figures, incumbent President Ellen Johnson Sirleaf is in the lead after last week's poll, with around 45 percent of the vote. Tubman has about 31 percent, and former rebel leader Prince Johnson about 11 percent.

In a statement Saturday, eight Liberian opposition parties said election officials had manipulated the results in favor of incumbent President Sirleaf.

Liberia's Election Commission has not responded directly to claims of fraud. It is calling on all parties to make complaints through proper legal channels.

Election observers from the Economic Community of West African States have said the October 11 vote was largely free and fair, and that ballot counting is proceeding smoothly. The U.S.-based Carter Center noted only minor irregularities.

Liberia's electoral commission has until October 26 to announce final results of the first round of voting.

The vote was Liberia's second national election since the end of a 14-year civil war in 2003.