United Nations Secretary General Ban Ki-moon has criticized the leaders of the world's wealthiest countries for failing to attend a pivotal humanitarian summit in Turkey.

At the closing of the World Humanitarian Summit in Istanbul, Ban said it was "disappointing that some world leaders" could not attend, singling out the Group of Seven countries.

The group includes Canada, France, Germany, Italy, Japan, the United Kingdom and the United States. Only Germany's Chancellor Angela Merkel attended the summit.

"The absence of these leaders from this meeting does not provide an excuse for inaction," Ban said. "They have a unique responsibility to pursue peace and stability."

The summit, which aimed to boost humanitarian responses to global crises, drew the participation of 65 heads of states.