Worldwide debt has risen to a record $226 trillion - more than three times global annual economic output - and firms in more countries are struggling to service loans, a study shows, just as key central banks prepare to end super-cheap credit policies.

World markets are expected to get confirmation over the next week that normalising global interest rates from the extraordinarily low levels introduced to offset the fallout of the 2009 credit crash is no longer just a U.S. phenomena.

The European Central Bank will lay out cuts to its 2-1/2 year-old stimulus programme on Thursday, the Bank of England looks set to raise British interest rates for the first time in a decade, while the Fed is moving towards its third hike of the year.

Years of cheap central bank cash has pushed world stock markets to successive record highs. But another side effect has been explosive credit growth as households, companies and governments took advantage of rock-bottom borrowing costs.

Global debt now amounts to 324 percent of the world's annual economic output, the Institute of International Finance (IIF) said in a report on Wednesday.

One of the most authoritative trackers of global capital flows, the IIF report also highlighted "rollover" risks, especially in emerging markets that have borrowed in hard currencies such as euros and dollars.

It calculated around $1.7 trillion needs to be refinanced or paid back before the end of 2018 across developing economies. Such debts will become costlier to service if Western interest rates rise and currencies strengthen.

While U.S. interest rates have already been raised four times, the prospect of more alongside Europe's shift toward tighter monetary policy, have pushed two-year U.S. borrowing costs to a nine-year highs.

The IIF said the rise in indebtedness was largely down to a $3 trillion rise in debt levels across the developing world, which now have debt totalling $59 trillion.