Officials say preliminary results of Liberia's presidential runoff election are expected as early as Thursday.

President Ellen Johnson Sirleaf is poised to win a second term, while the opposition candidate, William Tubman, boycotted Tuesday's election over alleged fraud.

As Liberia awaited the final tally, the head of Liberia's national police, Marc Amblard, announced Thursday that his officers had fired live rounds at an opposition group on Monday, the eve of the vote.

Amblard said force was necessary to bring a deteriorating situation under control after officers faced off against members of Tubman's Congress for Democratic Change who were protesting in Monrovia, the capital.

His statement contradicts suggestions he made Monday that he had no evidence officers fired shots.

Amblard says he has not received any confirmation of casualties, but the opposition says some people were killed.

The police chief says the incident will be investigated.

Meanwhile, observers said voter turnout for Tuesday's poll was very low, sparking concerns that opposition supporters will reject the outcome and political violence will erupt.

Tubman dropped out of the race after accusing the country's electoral commission of fraud. He said Wednesday that his party will not accept the results, which are expected by the end of the week.

In an interview with VOA Wednesday, Tubman's running mate, George Weah, indicated the CDC will hold post-election protests. He said the protests will be peaceful, but added the government must protect everyone in the event of unrest.

President Sirleaf, Africa's first democratically elected female leader, handily won the first round of voting last month, but fell short of the majority needed to avoid a run-off.

Election observers said the first round of voting was generally free and fair.

This is Liberia's second presidential election since the end of the country's civil war in 2003. Mrs. Sirleaf won the Nobel peace prize this year for helping Liberia recover from the war.