The Syrian Arab Red Crescent says at least 2.5 million people are now displaced within Syria. The figure is more than double the number so far used by aid agencies.
More than 408,000 Syrians have fled to neighbouring countries, and more are fleeing every day, according to the United Nations Commissioner for Refugees.
An estimated 36,000 people have been killed since the uprising against President Bashar al-Assad began in March 2011.
On Friday, the UN said it believed up to 4 million people inside Syria would need humanitarian aid by early next year, up from 2.5 million.