MONROVIA, Liberia (CNN) -- Ellen Johnson-Sirleaf has been declared president of Liberia following runoff elections, having received nearly 60 percent of the vote.The declaration was made Wednesday by Liberia's National Electoral Commission, which investigated election fraud claims filed by Johnson-Sirleaf's rival, international soccer star George Weah.Johnson-Sirleaf is the first female elected president in Africa.Weah received slightly more than 40 percent of the vote, according to official results.Celebrations erupted in the streets of Liberia following the announcement, despite a ban by United Nations peacekeepers in the country. Residents chanted and yelled "Ellen, give us a chance -- it's your turn."CNN's Africa Correspondent Jeff Koinange said Liberia appeared to welcome the change after nearly 150 years of turmoil -- the last 14 in a brual civil war that left nearly 200,000 people dead. "The hard part comes after her inauguration, because expectations are very high. Her greatest challenge is rebuilding a shattered nation," he said.Some 15,000 U.N. peacekeepers are now ensuring calm in Liberia. No windowpanes remain in buildings on the streets of the capital, Monrovia, and electricity is a luxury only enjoyed by those who can afford generators. Roads are in disrepair.Last week, Liberia's National Election Commission opened an investigation into seven electoral fraud complaints filed by Weah's party.Officials representing Weah told AP he still refused to concede defeat, maintaining allegations of ballot-box stuffing and vowing to keep fighting the results in court."We are questioning the entire process," Eugene Magbe, the chairman of Weah's Congress for Democratic Change party, said. "The elections were fraudulent." International observers have said the elections were largely free and fair, with only a few small irregularities.Johnson-Sirleaf is a widowed mother-of-four who also has eight grandchildren.CNN Africa Correspondent Jeff Koinange contributed to this report.Copyright 2005 CNN. All rights reserved.This material may not be published, broadcast, rewritten, or redistributed. Associated Press contributed to this report.