They did not put a dollar figure on the initiative, but said it would ramp up resources to deal with the "enormous humanitarian and economic toll" that conflicts in Syria, Iraq, Yemen and elsewhere are taking on the region.
"The world today is witness to... The highest level of forced displacement since the Second World War," UN Secretary General Ban Ki-moon said in a statement.
"To address the scale and the nature of the conflicts, we need new approaches. It is important that the World Bank, as a close partner to the UN, and other international financial institutions, mainstream and actively invest in conflict-affected states."
Under the first mechanism, guarantees from donor countries will be leveraged to issue special bonds, including Islamic sukuk bonds, which are specially structured to comply with the Koranic prohibition on charging interest.
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In the second, donor country grants will be used to extend low-interest loans to the countries hosting the bulk of the more than 15 million refugees who have fled the region's conflicts in the past four years.
"Strong global partnerships and innovative financing are essential to meet the scale of the need in these hard-hit countries," said World Bank president Jim Yong Kim.
The initiative was agreed on the sidelines of the annual meetings of the World Bank and the International Monetary Fund in Lima, Peru this week.
The organizations have set up a working group and asked it to finalise the details of the new financing mechanisms, as well as develop an implementation roadmap by February 2016, they said.