The number of Syrians forced to flee their country as a result of the civil war that began in 2011 topped 3 million on Friday, the U.N. refugee agency said.

"There are worrying signs too that the journey out of Syria is becoming tougher, with many people forced to pay bribes at armed checkpoints proliferating along the borders," the agency, known as the UNHCR, said in a statement.

"Refugees crossing the desert into eastern Jordan are being forced to pay smugglers hefty sums ($100 a head or more) to take them to safety," the statement continued.

Nearly half the Syrian population have been driven from their homes, including around 6.5 million internally displaced people, the UNHCR said.

The U.N. agency also noted that shifting frontlines in the multisided conflict are driving people out of areas that were previously unaffected.

The situation in Syria "has become the biggest humanitarian emergency of our era, yet the world is failing to meet the needs of refugees and the countries hosting them," U.N. High Commissioner for refugees Antonio Guterres said.

While the UNHCR has received more than $4.1 billion in donations for Syrian relief efforts since 2012, the agency said it needs an additional $2 billion by year's end. EFE