More than 30 humanitarian organisations have launched an appeal for countries to take in about 180,000 refugees from the Syrian conflict.

That figure would represent five per cent of the projected refugee population by the end of 2015, according to the Office of the UN High Commissioner for Refugees (UNHCR).

The issue will be discussed at a conference in Geneva on Tuesday.

After three years of fighting in Syria, more than 3.2 million refugees are registered in neighbouring countries. Turkey and Lebanon, for example, each host more than one million registered refugees.

With little sign of the conflict coming to an end, the UNHCR believes the number could rise to almost 3.6 million by the end of 2015.

If countries would take in 180,000 refugees, and an accompanying aid package and economic support was provided to the nations that open their doors, "it would also encourage those countries to keep their borders open to ensure those in Syria can flee the conflict, and could contribute to their stability", the UNHCR said.

"Syria's neighbouring countries have shown incredible generosity over the last three and a half years, but the strain of the crisis is weighing heavily on infrastructure and public services."

The UN refugee agency called on countries which have not accepted any refugees so far, such as the Gulf states and Latin American countries, to do their bit.