US security chief says terror threat possibly highest since 9/11 attacks

WASHINGTON - The United States is facing "heightened" threats of attacks from extremists, possibly the highest since the attacks of Sept 11, 2001, the head of US homeland security told lawmakers on Wednesday.

"There is no question that we have made many important strides in securing our country from terrorism since 9/11, but the threat continues to evolve," Homeland Security Secretary Janet Napolitano told a congressional panel.

"And in some ways, the threat today may be at its most heightened state since the attacks nearly 10 years ago."