Investors for weeks have been anxious that problems in developing economies could lead to broader trouble in financial markets. Turmoil in Turkey has been the most frequent cause for concern.

The jitters intensified on Thursday, yet the catalyst was not Turkey but Argentina — a sign that the array of challenges facing emerging markets might be spreading. The fears triggered a plunge in the currencies of multiple developing economies.

The Turkish lira and the South African rand dropped against the dollar, but it was the Argentine peso that experienced the most extreme fall, driven by fears the country would not be able to make its debt payments. Trying to halt the plunge in the value of the peso, which is down close to 50 percent this year, Argentina’s central bank ramped up interest rates by 15 percentage points.

The move by Argentina’s central bank brings its benchmark lending rate to 60 percent. It came a day after the country’s president, Mauricio Macri, said he had asked the International Monetary Fund to release $50 billion in credit earlier than had been agreed.