The global financial safety net has become increasingly fragmented, making it harder to respond to crises in a world roiled by volatile capital flows, International Monetary Fund (IMF) staffers warned.

Defenses haven't kept up with the growth of external debt in recent years, the Washington-based fund said in a report released Thursday. As a result, a system-wide shock could overwhelm the world's crisis resources, which include nations' foreign-exchange reserves, central-bank swap lines, regional funds such as the euro area's European Stability Mechanism, and the IMF itself, the lender said.

Financial cycles have been “growing in amplitude and duration, capital flows have become more volatile, and non-banks have gained importance, altering the nature of systemic risk,” IMF staff said in the report, which was presented to the fund's executive board on March 7. In a major event, “the needs could exceed the collective resources available,” the fund said.