UNITED NATIONS - Speakers at a panel highlighting Syrian President Bashar Assad's use of barrel bombs say the deadly explosives that target civilians are the main driver behind the ongoing refugee crisis.

Kenneth Roth, the executive director of Human Rights Watch, urges the international community to put an end to Assad's indiscriminate use of barrel bombs.

Raed Saleh, head of the Syrian Civil Defense, says : "We are tired of collecting limbs."\

They were among speakers at the U.N. Monday as part of a special event on use of the bombs by Syria's embattled government.

Human rights groups say barrel bombs are makeshift shrapnel-packed explosive devices that Syrian forces drop on rebel-held neighborhoods from helicopters, killing thousands of civilians.