Liberian President Ellen Johnson-Sirleaf has sacked her maritime chief, head of one of the country's main revenue generating agencies, for lying about allegations of fraud against him, officials said on Monday.

Johnson-Sirleaf appointed John Stewart as acting Commissioner of Maritime only last week without realising he was accused of defrauding clients in the United States while working there as a lawyer, her spokesman said.

"The president has relieved Mr John Stewart of his post ... He was relieved because he misled the president in providing information to her," Johnson-Sirleaf's press secretary Cyrus Badio told Reuters.

Liberia maintains the world's second biggest flag of convenience registry in the world after Panama, a major source of income for the impoverished West African country as it recovers from a 14-year civil war which ended in 2003.

Johnson-Sirleaf, a Harvard-trained economist who won elections in late 2005 to become Africa's first elected female head of state, has made fighting corruption one of the cornerstones of her efforts to rebuild Liberia.