The United Nations refugee agency says it has now registered two million refugees from the conflict in Syria - double the number of just six months ago.
At least 700,000 have fled to Lebanon, and more Syrians are now displaced than any other nationality, the UNHCR says.
UN High Commissioner for Refugees Antonio Guterres says it is essential to stop the conflict spilling over into neighbouring countries and causing what he calls an explosion in the Middle East, the BBC reports.
In a statement on Tuesday the UNHCR said: "Syria is haemorrhaging women, children and men who cross borders often with little more than the clothes on their backs."
About half of those forced to leave are children, UN agencies estimate, with about three-quarters of them under 11.
Just 118,000 refugee children have been able to continue in some sort of education, and only one-fifth have received some sort of counselling, with agencies warning of a "lost generation" of child refugees ill-equipped to help rebuild Syria in the future, the BBC reports.
Lebanon has received the highest number of refugees, even though it is the smallest of Syria's neighbours and one of the least able to cope.
There is now thought to be one Syrian refugee in Lebanon to roughly every six Lebanese. Jordan and Turkey have taken in the second and third highest numbers respectively.
As well as those who have left the country, a further 4.25 million have been displaced within Syria, the UNHCR says, meaning that more Syrians are now forcibly displaced than is the case with any other country.
Pointing out that more than 97% of Syria's refugees are being hosted by countries in the surrounding region, the UNHCR says the influx is "placing an overwhelming burden on their infrastructures, economies and societies".
It once again appealed for "massive international support" to help neighbouring countries deal with the crisis.
NZ agencies urge Govt to step up support
Seven New Zealand aid agencies are urging the Government here to back all possible means for a peaceful solution to the conflict rather than a military strike.
The Council for International Development includes charities Oxfam, Save the Children and World Vision amongst others.
They say the political options haven't been exhausted yet but not enough pressure is being put on the UN Security Council to push for negotiations.
Council director Dr Wren Green says the reports the Syrian government attacked its own citizens seem to be credible.
He told Checkpoint the international community needs to step up and work harder to bring all parties to the negotiating table.
Mr Green says refugees on the border of Syria and Lebanon are saying they don't want military action, they just want peace so they can go home.
Another UN official has issued a warning about the worsening Syrian conflict.
Mokhtar Lamani, a UN envoy to Syria, says the violence is pushing the country towards genocide. He says the growth in sectarianism is frightening.
Mr Lamani told the BBC in Damascus that the group most at risk is the Alawite minority, to which President Bashar al-Assad belongs.