Russia has the highest concentration of debt issuers at risk of downgrade of any emerging market country, according to ratings agency Standard and Poor's (S&P).

Across developing countries in Asia, Eastern Europe, the Middle East, Africa and Latin America, Russia had the greatest concentration of entities – be they companies, state institutions or government -- poised for downgrades, according to a research paper from S&P on Friday.

"Falling commodity prices and increased geopolitical concerns gave Russia the highest concentration of potential downgrades, at 27 issuers," S&P said.

Countries and businesses across emerging markets that were at risk of downgrade were rated from AA-minus down to B-minus that had either negative rating outlooks or ratings on "CreditWatch" with negative implications.

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