Obama threatens Syria of tough US response if chemical weapon claim true

President Barack Obama has said the alleged use of chemical weapons in a brutal attack on Syria on Wednesday is a matter of grave concern and required immediate attention, if proved true by the United Nations.

Obama said that country's core national interests were at stake in the Syrian conflict, while they want to curtail the proliferation of weapons of mass destruction as well as protect their allies in the region, BBC reports.

Opposition has confirmed that more than 1,000 were killed in the Damascus attack.

Obama, however, said the U.S. was seeking confirmation from the UN, if such weapons were used.

Earlier, Obama had warned Syria that using chemical weapons would force a tough U.S. response.

According to the report, Syrian authorities have not yet confirmed that they will allow a UN inspection team to investigate the claims or not.

Meanwhile, Syria's main ally Russia has said new evidences had started to emerge, which made it clear that Syrian rebels had provoked the government for the attack.

BBC has learnt that the White House regards Wednesday's attack on Damascus suburbs as an outrage that breached international law and demands a response.