A new Global Terrorism Index annual report claims Boko Haram in Nigeria is the world's deadliest extremist group, with the grim honor of having killed more people than ISIS (or "Daesh"), to which it is linked.

According to the report published by the New York City-based Institute for Economics and Peace, deaths attributed to Boko Haram increased 317$ in 2014 to 6,644.

The report lists 6,073 deaths attributed to ISIS. In March, 2015, Boko Haram pledged allegiance to ISIS, dubbing itself the West Africa Province of Islamic State.

Both groups are said to be responsible for 51% of all global terrorism killings.

Amnesty International says Nigeria's military is responsible for an additional 8,000 deaths in detention.

Most terrorist attacks take place in countries with governments that routinely commit political violence, the report found.

Boko Haram is believed responsible for an attack in Nigeria this week that killed more than 30, and may have wounded another hundred people.

ISIS took credit for a recent series of attacks in Paris that killed over a hundred, with scores injured.