Liberia’s Unity Party (UP) has accused President Ellen Johnson-Sirleaf of interfering in the vote.

UP, Liberia’s ruling party candidate finished runner-up in the first round of this month’s presidential election.

Reacting to the circumstances surrounding the poll, Unity Party said in a statement that the October 10 poll, meant to usher in Liberia’s first democratic transition of power since 1944, was "characterised by massive systematic irregularities and fraud".

The statement, read to reporters by Unity Party Chairman, Wilmont Paye, said Johnson-Sirleaf had acted inappropriately by meeting privately with elections magistrates before the vote.

"Greed has resurfaced in its most callous form, sowing seeds of discord yet again with the intent of disrupting the fragile peace of Liberia," the party said in its statement.

Unity Party officials said they were supporting a legal challenge by Liberty Party of the third-place candidate Charles Brumskine, which has petitioned the elections commission for a re-run of the first round.

The All Liberian Party of businessman Benoni Urey also said on Sunday it was backing the complaint.

"It doesn’t mean we will not take part in the (run-off)," Augustine Ngafuan, Unity Party’s national campaign chairman, told Reuters.

"We hope the court can rule before the run-off. If not, we will decide what next to do."

An official from the elections commission said it expected to hear the formal complaint on Monday.

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The commission’s findings can be appealed in the Supreme Court.

At Johnson-Sirleaf’s residence, where she was celebrating her 79th birthday, her spokesman Jerolinmek Piah, told reporters that he would comment on the accusations later, as he did not want to overshadow the festivities.

International observers from the European Union, the Carter Centre and the National Democratic Institute have said they saw no major problems with the vote.

Unity Party’s statement cements a falling out between Johnson-Sirleaf, a Nobel Peace Prize laureate, and her party’s leadership after 12 years in power that saw the country consolidate a post-war peace but it also drew sharp criticism over alleged corruption and underdevelopment.

Joseph Boakai has served as Johnson-Sirleaf’s vice president since the president’s inauguration in 2006.

However, Johnson-Sirleaf declined to endorse him and he distanced himself from the last administration.

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George Weah, a former soccer star in Europe, won the first round with 38.4 per cent of the vote to Boakai’s 28.8 per cent and has momentum heading into the run-off.

On Thursday he picked up the endorsement of former warlord Prince Johnson, who won eight per cent of the vote in the first round.

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