The International Monetary Fund warned on Thursday that China’s emergence as an alternative lender was creating a new wave of hidden debt in Africa as it backed its companies’ expansion overseas with increasingly aggressive lending.

Adnan Mazarei, a director at the fund, said action was needed “to avoid another round of debt accumulation” as emerging lenders such as China became an important source of funds. An IMF official said that while it was working to strengthen surveillance, the fund did not have precise numbers or details about the amounts borrowed by poor countries.