US Democratic presidential candidate Hillary Clinton Saturday hit back at her Republican rival Jeb Bush over his remarks that President Barack Obama's decision to bring back US troops in Iraq led to the rise of the Islamic State.

"I find it somewhat curious that Jeb Bush is doubling down on, defending his brother's actions in Iraq," Clinton said at a news conference during a campaign stop in Iowa.

"If he's going to do that, he should present the entire picture. And the entire picture, as you know, includes the agreement George W. Bush made with the Maliki government in Iraq that set the end of 2011 as the date to withdraw American troops."

During the past week, Republican candidate Jeb Bush, believed by many as the front-runner in the crowded Republican field, launched aggressive attacks for at least two times at Obama and Clinton, accusing the pair of poorly handling the Iraqi war.

"That premature withdrawal was the fatal error, creating the void that ISIS (IS) moved in to fill," said Bush at a late Tuesday rally in California, referring to the Obama administration's decision to bring back US troops in Iraq in 2011.

Currently, there are about 3,500 US troops in Iraq, the majority of whom are providing military training to Iraqi forces.

Jeb Bush's accusations against Hillary Clinton over Iraq came as no surprise as the Republicans widely perceive foreign policies as the possible vulnerability of Clinton, who helmed the State Department during Obama's first term in office and was currently dogged by controversy surrounding her suspicious emailing practice.

However, Bush's proactive moves in reviving the memory of a flawed and unwelcomed war sponsored by his brother and former President George W. Bush risk bogging him down in a debate that could make voters question his independence from the policy of other members of the Bush family.

Earlier this year, Jeb Bush stumbled over questions about the Iraqi war and spent a whole week coming up an answer to the question whether, "knowing what we know now," he would have invaded Iraq.