Ghana is asking some of the nation’s largest companies to pay millions of dollars in back taxes as the cash-strapped government scrambles to raise money and finalize a bailout from the International Monetary Fund.

Gold Fields Ltd. and Kosmos Energy Ltd. have been told they owe back taxes, as have Tullow Oil Plc and Africa’s largest wireless carrier MTN Group Ltd. All of the companies dispute the government’s claims. Ghana has been forced to allocate most of its revenue to service an estimated 576 billion cedis ($48 billion) of public debt.

“Ghana is clearly facing fiscal and economic challenges at the moment,” Gold Fields spokesman Sven Lunsche said in an emailed response to questions. “We are hopeful that the government will not resort to unreasonable fiscal measures that will further imperil the challenges facing the corporate sector.”

West Africa’s second-largest economy lost access to international capital markets because of its ballooning debt and loan-service costs. It’s restructuring most of its obligations amid a slump in the cedi, and is seeking a $3 billion loan from the IMF.

Gold Fields is in talks with the country’s tax authority to try and resolve the demand for 2018 to 2020. MTN, which has been ordered to pay $776 million, has until Friday to reach an agreement with the Ghanaian authorities.

Kosmos Energy, headquartered in Dallas, said the authorities claimed the company underpaid certain taxes and other contractual fiscal obligations. The claim is without merit and Kosmos will “vigorously dispute” it if required. Both Gold Fields and Kosmos declined to give financial details.

A spokeswoman for the Ghana Revenue Authority declined to comment when contacted by phone.