Fewer countries faced terrorism threats last year than in 2012, but the severity of the threats sharply increased in some areas, according to Aon P.L.C., which published its 2014 Terrorism and Political Violence Map on Tuesday.

The number of countries with identifiable terrorism perils in 2013 decreased by 12% to 80 compared with 2012, according to Aon.

While 34 countries saw their country risk scores for terrorism and political violence decrease during 2013, the threat of terrorism and political violence in some of those countries already rated as having a “severe” or “high” risk of attack worsened during the year, said Henry Wilkinson, head of the intelligence and analysis practice at the London-based Risk Advisory Group P.L.C., which helped Aon to produce the map.

Despite signs of economic recovery in many countries, businesses operating in emerging economies are exposed to risks fueled by the uneven recovery, Mr. Wilkinson noted.

A core trend is the widening gap in terrorism and political violence risk between developed economies and emerging markets, Mr. Wilkinson said at a briefing Tuesday.

In addition, he said, the phenomenon of “social media-driven wildfire unrest” was adding to the risks faced by companies and contributed directly to an increase in the country risk ratings of Brazil and Turkey for 2014, for example.

Terrorist attacks increased by 75% in Russia in 2013, raising concerns about the threat to the upcoming Sochi Winter Olympic Games, Mr. Wilkinson said.

Overall, Russia is rated as having a “medium” risk of terrorism and political violence, according to the map.

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The Middle East and North Africa is the region most at risk from terrorism and political violence, according to Aon, and was the subject of 52% of all known terrorist attacks and plots during 2013.

During 2013, retail companies were affected the worst by terrorist attacks, the map shows, with 33% of all attacks hurting business affecting the sector.

The transportation sector was affected by 18% of all attacks in 2013, while 12% of all attacks hit the oil sector, and 6% hit the electricity and infrastructure sector, according to the map.