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Financial markets are experiencing an "uneasy calm", according to the Bank for International Settlements, a central bank association.

In the bond market, "a number of anomalies suggest that all is not well," said Claudio Borio, the head of the monetary and economic department at BIS.

He also warned the amount of bad loans in the eurozone is "too high".

Any forthcoming US rate hike could harm emerging economies, said BIS.

"Less favourable financial market conditions," together with a weaker outlook for the global economy "and increased sensitivity to US interest rates, heighten the risk of negative spillovers" into emerging economies once the US does decide to raise interest rates, it said.

'Increased risk'

A rise in the dollar's value that may accompany a rate rise could lead to loans made in dollars in these countries becoming less affordable.

Loans in dollars to emerging economies - which would include Brazil, China, Russia and India - doubled since 2009 to more than $3tn (£1.99tn) said BIS.

"Despite low interest rates, rising debt levels have pushed debt service ratios for households and firms above their long-run averages, particularly since 2013, signalling increased risks of financial crises" in emerging market economies, it said.

The International Monetary Fund downgraded its forecast for global economic growth in October.

It reduced its figure for 2015 to 3.1% from the 3.3% it predicted in July. The 2016 forecast is down to 3.6% from 3.8%.

US rates decision

The Federal Reserve's Federal Open Market Committee, which decides on monetary policy including rates, opted in October to keep US interest rates unchanged, at record lows of 0% to 0.25%, the same level they have been at since December 2008.

It meets again on 15-16 December.

Mr Borio noted that "financial institutions, notably banks, are not using their balance sheet capacity as they once did."

Concern has been growing about the corporate bond market and the ability for investors to be able to buy and sell corporate debt.

A lack of buyers could lead to a crisis in the corporate bond market, the head of money manager Aberdeen Asset Management, Martin Gilbert told the BBC on 30 November.