Liberian President Ellen Johnson Sirleaf holds an unassailable lead in the country's election run-off over rival Winston Tubman.With 86% of polling stations reporting, Mrs Sirleaf was headed for re-election with more than 90% of the vote.Mr Tubman, who had urged supporters to boycott Tuesday's vote, won 9%, the National Election Commission said.He has alleged the election process was rigged in favour of Mrs Sirleaf, a charge international observers deny.Turnout was 37.4% - about half the number who turned out for the election's first round last month.Mrs Sirleaf won the most votes in that round, but failed to gain an outright majority, forcing a run-off.With such a low turnout and no majority in parliament, her task promises to be all the more difficult, says the BBC's Thomas Fessy in the capital, Monrovia.She said she would reach out to all presidential candidates to work within an inclusive government."What I will offer them is not yet known," she told reporters on Thursday. "I am confident we will be able to reconcile the people."But Mr Tubman said he would not participate in her administration, our correspondent says.The run-up to Tuesday's voting was marred by violence in which two people were killed when security forces opened fire. Mrs Sirleaf has promised an investigation.International observers said the election process was credible and transparent.