ISIS bigger threat to US than Al Qaeda: FBI chief

The FBI chief has warned that the Islamic State has become a bigger threat to the United States than the Al Qaeda as the dreaded group has influenced a significant number of Americans through social media and instructed them to carry out attacks in their own country.

"ISIS has become a bigger threat to the United States than the Al Qaeda," FBI Director James Comey said, referring to the threat of growing "lone wolf" terrorists at home.

Speaking at the Aspen Security Forum, Comey said the ISIS has influenced a significant number of Americans through social media instructing them to kill where they are instead of travelling to the Middle East.

ISIS or IS is an Al-Qaeda splinter group and it has seized hundreds of square miles in Iraq and Syria.

The Al Qaeda has distanced itself from the group, chiding it for its lack of teamwork in its aggressive, brutal expansion.

Talking about the last week's incident in which four marines and one sailor were killed when 24-year-old Mohammad Abdulazeez opened fire on two military centers in Chattanooga, Tennessee, the FBI director said, "Investigators haven't determined why Mohammad Abdulazeez carried out the shootings."

The FBI is determined to "understand every second of his life" for the last two years, at least, Comey was quoted as saying by CNN.

Militants from groups affiliated with once feared al- Qaeda network are abandoning their outfits to join the ISIS that has declared an Islamic "caliphate" in territory it controls in Syria and Iraq.

ISIS leaders have described al-Qaeda as a "drowned entity" and declared that they will not tolerate any other jihadi group in territory where they are operating.

The group led by Abu Bakr al-Baghdadi, a former Al Qaeda commander in Iraq, has gone on to build a global network of affiliates and branches that now stretches from Afghanistan to West Africa.