Syria's six-year conflict has caused losses of $226 billion (Dh830bn) to its economy, according to estimates published by the World Bank on Monday.

The number of casualties is devastating, but the war is also destroying the institutions and systems that societies need to function, and repairing them will be a greater challenge than rebuilding infrastructures, World Bank vice president for the Middle East and North Africa Hafez Ghanem said.

The World Bank report found that cumulative GDP losses since Syria's conflict erupted have been estimated at $226bn, about four times the Syrian GDP in 2010.

It estimated that the conflict had damaged or destroyed 27 per cent of Syria's housing stock and about half the country's medical and educational facilities.

Those calculations were based on cross-checked satellite imagery of certain cities and areas and extrapolated based on a conflict intensity model.

The World Bank also found an average of 538,000 jobs had been lost annually between 2010 and 2015. It said more than three in four Syrians of working age - or about nine million people - were neither employed nor enrolled in any form of school or training.

The long-term consequences of this inactivity will be a collective loss of human capital leading to a shortage of skills in Syria, it said.

The World Bank report came as the UN envoy to Syria Staffan de Mistura opened the seventh round of indirect talks in Geneva between Syrian government representatives and opposition leaders to try to end the country's conflict.

UN-brokered talks for Syria had been going on for a long time prior to the Astana talks which started in January. UN-backed talks have not borne fruit due to intransigence by Saudi-backed groups.

De Mistura estimated in August last year that more than 400,000 people had been killed in the war until then. The UN has stopped its official casualty count in the war-torn country, citing its inability to verify the figures it receives from various sources.

The conflict in Syria started in March 2011, with the government of President Bashar al Assad blaming some Western states especially the US and its regional allies particularly Saudi Arabia and the Israeli regime of backing Takfiri terrorists wreaking havoc in the country.