FEARS are growing for thousands of refugees who have fled the civil war in Syria as they face bitter winter weather huddled inside thin plastic tents.

Having survived a conflict in which more than 40,000 people are estimated to have been killed, refugees at centres such as the Bab al Salameh camp on the Syrian-Turkish border say the winter is now a bigger threat to them than the violence engulfing their country.

"The situation here is even worse than being at home," said Waad Orfali, dressed in a pink headscarf, velvet pink gown and slippers, as rain pounded the camp.

"At least in the village there was a doctor," said the 27-year-old, who escaped from the northern village of Marea about two weeks ago after snipers and air strikes forced her and her family to relocate to the relative safety of the camp.

The flimsy tents scattered across the encampment offer scant relief to the thousands of men, women and children facing freezing weather and constant rain, with colder conditions still to come.

Earlier this month, the United Nations refugee agency said more than half-a-million Syrian refugees are registered or waiting in other Middle Eastern countries, with about 3000 new people seeking refugee status and assistance daily.

"I'm three months pregnant," said Orfali, who suffered from mouth sores.

She said her husband suffered from kidney stones, but that neither had been able to receive medical care at the camp.

With blankets, clothes and rugs soaked as the rain seeps in, and with no electricity in the camp, children, many wearing a single layer of clothing and slippers with no socks, shiver in the cold.

IHH, a Turkish relief group, is running the camp which houses 6000 people.

As the war continues, more Syrians are expected to flee.

The latest estimates indicate the total number of Syrians who have fled during the conflict has already surpassed the 700,000 refugees the UN forecast by year-end, although more than 200,000 of them have not registered formally. Another 2.5 million or more are believed to be displaced inside Syria.

Meanwhile, Israel voiced doubts about the accuracy of Syrian activists' reports that chemical weapons had been used against rebels fighting to topple President Bashar Assad.

"We have seen reports from the opposition. It is not the first time. The opposition has an interest in drawing in international military intervention," Vice Prime Minister Moshe Yaalon said on Army Radio.

"As things stand now, we do not have any confirmation or proof that (chemical weapons) have already been used, but we are definitely following events with concern," he said.

The Syrian Observatory for Human Rights gathered activist accounts on Sunday of what they said was a poison gas attack in the city of Homs.

The reports are difficult to verify, as the Government restricts media access in Syria.

The Observatory, a UK-based group with a network of activists across Syria, said those accounts spoke of six rebel fighters who died after inhaling smoke on the front line of Homs's urban battleground.

It said it could not confirm that poison gas had been used and called for an investigation.