The current turmoil in Iraq was directly caused by the 2003 U.S.-led invasion, ex-U.N. Secretary General Kofi Annan told RT in a new interview.

"You cannot disassociate the situation in Iraq today from the US intervention of 2003. Because not only did the intervention take place, but they dismantled the Iraqi Army, which was the tool of Saddam to maintain law and order," Annan, who was U.N. chief between 1997 and 2006, told RT.

"The civil service, the Baathist Party were all [dismantled]. So the structures and state institutions vanished overnight, creating a very serious vacuum, which has led to where we are today. So I don't think anybody can argue with that. The link is clear."

The Islamic State group filled that vacuum as they rapidly and ruthlessly expanded across Syria and Iraq in 2014, imposing radical Sharia law on vast swaths of land and murdering anyone who disobeyed. The U.S. and a number of other countries, including Iran, Syria, Saudi Arabia, Bahrain, Jordan, Qatar, the United Arab Emirates, subsequently launched new ongoing military campaigns in the area to wipe the group out.

Annan opposed the invasion when it was launched in 2003 as well, calling it unequivocally illegal.

"I have indicated it was not in conformity with the UN charter. From our point of view and from the charter point of view it was illegal," he said in a 2004 interview.

Since then, it's been discovered that former President George W. Bush and his administration publicly made at least 935 false statements in the run-up to the war, according to an investigation conducted by the Center for Public Integrity and its affiliated group, the Fund for Independence in Journalism.

"In short, the Bush administration led the nation to war on the basis of erroneous information that it methodically propagated and that culminated in military action against Iraq on March 19, 2003," the report reads.

According to a report released in March by the Nobel Peace Prize-winning doctors' group Physicians for Social Responsibility, those lies resulted in the death of at least 1.3 million civilians, and as many as 2 million. Another study from 2010 found dramatic increases in infant mortality, birth defects and cancer in Iraq, at rates greater than those found after atomic bombs were dropped on Hiroshima and Nagasaki in 1945.

Annan told RT that he believes one of the U.N.'s greatest failures is that it didn't give smaller nations more of a platform to voice concerns about world affairs, and that it didn't hold world powers like the U.S. accountable for their actions.

"But what is interesting," Annan continued, "is that the big powers are not members of the [International Criminal Court], and yet they sit in the Security Council and refer smaller countries and others to the Court."

"In effect, [they are] saying we are going to apply the law to the small people and the small countries, but we would absolve ourselves, it wouldn't apply to us. What sort of justice is that? It has to be, we have to aim for a system, and a legal system where the laws are applied fairly and consistently across the board," Annan said.