According to UN refugee agency, the number of Syrian refugees has been risen to two millions in Turkey as the Syrian refugee number in Iraq and Lebanon declined in August.
The Syrian refugee count in Turkey has jumped by more than 200,000 since June, having risen by just 14,000 in the previous three months, UNHCR spokeswoman Selin Unal said.
Unal said Turkish authorities were trying to stop people reaching Europe. Syrians who were found making their way through Turkey were stopped and registered as refugees.
From Turkey, tens of thousands of refugees try to reach Europe by attempting the short sea crossing to Greece, though many have drowned on the way.
However, she said it was impossible to say that the spike in refugee numbers in Turkey was due to people moving towards Europe. It could have been caused by Syrians who had been in Turkey for some time deciding to register as refugees.
In Lebanon, a recount of refugee numbers last month removed almost 60,000 from the tally of Syrians there, taking the total down to 1,113,941.
In Iraq, the decline in the numbers was small -- 3,747 left while 3,151 arrived during August -- leaving the population of Syrian refugees at 249,463. But any fall in refugee numbers is unusual because of the relentless outflow from Syria, where the war shows no sign of stopping after more than four years.
Unlike Lebanon and Jordan, which have effectively closed their borders to new Syrian refugees, Iraq is still open to those fleeing from ISIS or fighting between the government and opposing armed groups.
Many of those leaving Iraq told UNHCR they were returning to Syria because of the high cost of living and lack of jobs in Iraq's Kurdistan region, or for family reunions and improving conditions in their former home regions.
However, there had been a sharp increase in people saying they were heading to Turkey and onwards to other European countries, and UNHCR said people-smuggling had been frequently reported in all refugee locations in Iraq.
"Camp authorities have for instance reported the departure at Basirma camp of 30 head of households to Turkey, leaving wives and children behind," a UNHCR report said, adding that the smuggling route ran through the Balkans and ended in Germany.
A UNHCR mission to the Sarziri border post into Turkey reported that "illegal crossings by Syrians continue through the mountains, with numbers reaching an average of 10-15 individuals intercepted per week", the document said.
UNHCR data showed 428,735 Syrians applied for asylum in 37 European countries between the start of the war in early 2011 and August this year, an increase of 60,000 since July.
The International Organization for Migration (IOM) said on Tuesday that an estimated 464,876 refugees have now crossed the Mediterranean so far this year, up from 432,000 as of Friday. That is more than twice the total for the whole of 2014.