More than two million Syrians have fled their country, the UN refugee agency (UNHCR) said Tuesday, amounting to a tenth of Syria’s population. In addition, over four million Syrians are also displaced inside the country.  

The grim refugee statistics were described by Antonio Guterres, the United Nations High Commissioner for Refugees, as a “disgraceful humanitarian calamity with suffering and displacement unparalleled in recent history.”

He told reporters in Geneva the two-million milestone – which represents a nine-fold increase in 12 months – was not just an appalling statistic, but represents “two million individual stories. Two million people, many have lost their houses, members of their families, their possessions.”

“The risks for global peace and security that the present Syria crisis represents, I’m sure, are not smaller than what we have witnessed in any other crisis that we have had since the Vietnam war,” said Guterres, a former Portuguese prime minister.

On average, some 5,000 Syrians flee their country every day, according to his agency.  The majority of refugees have fled to Lebanon and other neighboring countries with the flow of refugees gathering momentum in recent weeks amid fears of a US-led strike on the Syrian regime.

On Monday the aircraft carrier USS Nimitz moved into the Red Sea signalling U.S. preparation for an attack on Syria, although President Barack Obama has faced criticism for hesitating to respond sooner to the deadly chemical attack his administration says killed over 1400 civilians in a Damascus suburb on August 21. Congress is set to vote on the issue in the coming days.