The United Nations High Commissioner for Refugees said Friday (August 3rd) that continued fighting in Syria could create a "gigantic outflow" of people on an unprecedented scale.

"We all have seen crises of this nature in different parts of the world," said UNHCR High Commissioner Antonio Guterres. "Let's hope this doesn't evolve into the kind of gigantic outflows we have witnessed in Afghanistan or Iraq."

"Obviously, if the conflict intensifies, the capacity to deliver [aid] will be more and more limited," he said, adding that "contingency planning" was in place "for more dramatic situations".

According to the UN refugee agency, an estimated 1.5 million people are internally displaced in Syria. Officials said intense violence in cities such as Aleppo remains the biggest challenge to aid efforts.

"It was impossible yesterday to send additional relief teams, as [Aleppo] was sealed off by military forces," said UNHCR spokeswoman Melissa Fleming. She said the agency confirmed there is a complete mobile telephone and internet blackout in the city.

The UN agency reported that on a single day, some 700 refugees approach relief workers in Damascus.

Thousands of refugees have already fled to Turkey, Lebanon, Iraq and Jordan while some 10,000 Iraqis in Syria decided to return home, the UNHCR said.