But another militant Islamist organization overtook ISIS to become the world's deadliest terrorist group last year,
according to a new report.
Boko Haram, the Islamic extremist group based mainly in Nigeria's northern states, 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. Internationally, deaths from terrorism experienced a "dramatic rise" in 2014, increasing by 80% from the previous year, according to the study by the Institute for Economics and Peace.
There were 32,658 people killed in terrorist attacks last year -- nine times more victims than there were in 2000, it says.