( CNN) With its reign of terror in the Middle East, its claim to have brought down a Russian passenger airplane and now, the atrocities in Paris, ISIS has commanded global headlines as the world's most dangerous terror group.

But another militant Islamist organization overtook ISIS to become the world's deadliest terrorist group last year, according to a new report .~ ATAGEND

Boko Haram, the Islamic extremist group based mainly in Nigeria's northern nations, was responsible for 6,644 deaths in 2014, an increase of 317% from the previous year, according to the Global Terrorism Index, released Tuesday.

By contrast, ISIS, the terror group to which Boko Haram reportedly pledged allegiance in March of this year, was responsible for 6,073 deaths.

Between them, the two groups were responsible for more than half( 51%) the deaths attributed to terrorism, in the deadliest year on record for terror, according to the report.

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