Liberia's opposition leader on Friday slammed the awarding of the Nobel Peace Prize to President Ellen Johnson Sirleaf days before going before the electorate as "unacceptable and underserving".

"Madam Sirleaf does not deserve a Nobel peace prize award because she committed violence in this country. This award is unacceptable and undeserving," her main opponent in next Tuesday's presidential election, Winston Tubman, told AFP by phone.