Acting Secretary of U.S. Homeland Security Elaine Duke has warned tha and al-Qaeda terror groups, both outlawed in Russia, are still plotting attacks of 9/11 scale.

“The threat is still severe. The terrorist organisations, be it ISIS or al-Qaeda or others, want to have the big explosion like they did on 9/11.

They want to take down aircraft, the intelligence is clear on that,” Duke warned.

The senior US official noted, nevertheless, that the jihadists preferred to resort to smaller plots.

“They are using small plots and they are happy to have the small plots. Creating terror is their goal.

“A bladed weapon attack causes terror and continues to disrupt the world but that does not mean they have given up on a major aviation plot,” Duke added.

IS and al-Qaeda terror groups have committed a number of deadly terror attacks across the world over the past few years.

The bloodiest one took place in Paris in November 2015, leaving 130 people dead and more than 400 injured.

On Sept. 11, 2001, al-Qaeda hijackers crashed two airplanes into the World Trade Center in New York City and one into the Pentagon in Washington, DC.

The fourth airplane crashed in Shanksville, Pennsylvania after the passengers tried to take back control of the plane from the terrorist hijackers.

Nearly 3,000 people were killed and another 6,000 were injured in the attacks. (Sputnik/NAN)