Terrorist attacks similar to those that struck New York and Washington on Sept. 11, 2001, are "probably no longer possible," European Union (EU) counter-terrorism coordinator Gilles de Kerchove said on Monday.

"I think we can say today that an attack of the scale and the sophistication that we once had on September 11 probably is no longer possible," he told reporters at a news conference for the 10th anniversary of the attacks.

However, he also stressed "That doesn't mean we are completely out of threat."

He said that al-Qaida, the terrorist group that allegedly masterminded the Sept. 11 attacks, had been significantly weakened by the striking campaigns in Afghanistan and Pakistan, which led to the death of its leader Osama bin Laden this year.

Kerchove warned that terrorist threat today is "more complex and diverse", referring to remnants of al-Qaida and terrorist groups in the Arabian Peninsula and North Africa.

In the last decade, international cooperation on fighting against terrorism has been strengthened by sharing data, collaborating in the fields of police and judiciary etc., Kerchove said, adding mechanisms and institutions within EU have been established for counter-terrorism.

"Overall, we are much better equipped today that we were 10 years ago," he said.

In addition, Kerchove said it was very important that terrorists should be brought to justice, rather than imprisoned or killed without trail.