The U.S. has chided Russia for what it calls an "unfortunate decision" to send missiles to the Syrian government, BBC News reported.

Chairman of the Joint Chiefs of Staff Gen Martin Dempsey said the shipment "will embolden the regime and prolong the suffering" that has killed 80,000.

The sophisticated anti-ship missiles could be used to counter any future foreign military intervention, U.S. officials told The New York Times.

Some 1.5 million people have fled the conflict, says the UN refugee agency. Most have fled to Jordan and Lebanon, but not all have been registered yet, meaning the true total is likely to be far higher, according to the UNHCR.

Meanwhile, Syria's national production has dropped by 40% and the number of people living below the poverty line has risen from two million to five million in just two years, according to the man in charge of the UN's plans for reconstructing Syria after the conflict.

Abdullah al-Dardari, a former deputy prime minister in President Bashar al-Assad's administration, told the BBC that rebuilding what has been destroyed would cost up to $80bn.