Syria's civil war and the spread of the so-called Islamic state has cost the Middle East around $35bn, according to a study by the World Bank.

The conflicts broke out at time when the region was becoming increasingly integrated, with cross border trade and investment rising before the Syrian conflict erupted in 2011.

Syria has lost 16% of its per capita welfare, while Iraq has lost 14%, according to figures in the study, "Economic effects of the Syrian war and the spread of the Islamic state on the Levant."

The Syrian war and the emergence of the Islamic state have "imposed enormous human, social and economic costs and put a halt to the regional trade integration process, thus undermining development with serious implications for the future of the Levant," the report concluded.

"The cumulative economic size of these economies, measured by their gross domestic product, could have been $35bn larger had the war not occurred," the report said.

The report does not address the economic costs of hosting refugees. More than 3 million Syrians have registered as refugees, with all but a few thousand residing in neighbouring countries.