THOUSANDS of Syrians have poured across the border to escape fighting in their battered homeland.

More than 170,000 Syrians have been registered in Iraq, Jordan, Lebanon and Turkey, according to UN aid agencies.

Some 3500 Syrians fleeing Aleppo, Azaz, Idlib and Latakia had arrived in Turkey by Wednesday, said Adrian Edwards of the UN High Commissioner for Refugees (UNHCR).

"There has been a further sharp rise in the number of Syrians fleeing to Turkey," he said.

"There are now almost 65,000 Syrians in nine camps in Turkey, though not all yet registered. To put this in perspective, about 40% arrived in August."

A Syrian air strike in the rebel-held border town of Azaz on Wednesday killed 30 people, according to a local doctor. Overnight, more than 1000 Syrians arrived in Jordan.

The UNHCR is working to improve the ratio of people to toilets – currently 40 to one – in the Za'atri camp, which holds nearly 8000 of 47,000 refugees.

The humanitarian situation in Syria has deteriorated as fighting escalates, cutting off civilians from food supplies, healthcare and other assistance.

Some 1.2 million people are uprooted within the country, many staying in schools or other public buildings, the UN said.

UN humanitarian chief Valerie Amos said on Thursday that up to 2.5 million people needed aid in the country, where President Bashar al-Assad's forces have been fighting rebels for 17 months.

There has been an outbreak of diarrhoea in part of rural Damascus because the water supply has been contaminated by sewage, the World Health Organisation (WHO) said.

"In one pocket there are 103 suspected cases of e.coli," said Richard Brennan of WHO's emergency risk management and humanitarian response department, adding: "Testing is still going on."