More than a million Syrian refugees who have flocked to Turkey are struggling to survive on their own, Amnesty International warned Thursday.

With Turkey's government-run refugee camps operating at full capacity and hosting half of the 3.2 million refugees who have fled Syria, Turkey is shouldering the heaviest burden of the refugee crisis.

"In three days in September 2014, Turkey received some 130,000 refugees from Syria - more than the entire European Union had in the past three years," Amnesty said.

It also detailed cases where Turkish border guards had abused or even killed refugees trying to enter the country.

An estimated 1.6 million Syrian refugees have entered Turkey since the war began in March 2011.

Around 220,000 are living in 22 government camps that offer food and essential services.

The remaining 1.38 million - more than 85 per cent - are living outside the camps, mostly in communities along the border.

An estimated 330,000 live in Istanbul.

So far, Ankara has spent £2.5 billion on Syrian refugees and granted free healthcare to all refugees in the country.

But while Turkey has an open-border policy for Syrian refugees, there are just two fully open crossings along the 560-mile border.

Even at those crossings, people without passports are being denied entry unless they have urgent needs.

Other refugees trek into Turkey through dangerous crossing points.

According to Amnesty, at least 17 people were shot and killed by border guards at unofficial crossing points between December 2013 and August.

The report cited 10 other incidents in which 31 people were beaten by border guards.

"Turkey is clearly struggling to meet even the most basic needs of hundreds of thousands of Syrian refugees," said Amnesty International spokesman Andrew Gardner.

"The result is that many of those who have made it across the border have been abandoned to a life of destitution."

The organisation urged Turkey to "radically revise its border practices and end the necessity for refugees to use dangerous irregular crossings."

Of the United Nations' funding appeal for $3.74 billion (£2.4bn) in aid, only 51 per cent has been received.