Six thousand people are fleeing Syria every day as the conflict intensifies and merges with violence in neighbouring Iraq, United Nations officials have said.
The warnings were given on Tuesday at a rare public briefing of the UN's Security Council in New York
The High Commissioner for Refugees, Antonio Guterres, told the meeting that the organisation had "not seen a refugee outflow escalate at such a frightening rate since the Rwandan genocide almost 20 years ago".
Ivan Simonovic, the Assistant Secretary-General for Human Rights, told the meeting that at least 92,901 people were killed in Syria - among them more than 6,500 children - between March 2011 and the end of April 2013.
"The extremely high rate of killings nowadays - approximately 5,000 a month - demonstrates the drastic deterioration of the conflict," Simonovic told the council meeting.
Guterres said that two-thirds of the nearly 1.8m refugees registered with the UN in Lebanon, Turkey, Jordan, Iraq, Egypt and elsewhere had left Syria since the beginning of the year.
The UN envoy to Iraq, Martin Kobler, later gave warning that escalating violence in Iraq could no longer be separated from the war in Syria because "the battlefields are merging".
Kobler said Iraqi armed groups had an increasingly active presence in Syria and as a result, the Syrian conflict is no longer just spilling over into Iraq, but Iraqis are reportedly taking arms against each other inside Syria.
"These countries are interrelated," Kobler stressed. "Iraq is the fault line between the Shia and the Sunni world and everything which happens in Syria, of course, has repercussions on the political landscape in Iraq."
Kobler said the last four months have been among the bloodiest in Iraq in the last five years with nearly 3,000 people killed and over 7,000 injured.
The Security Council has been deadlocked on Syria.
Russia, an ally of Syrian President Bashar al-Assad, and China have three times blocked action against Assad that was backed by the remaining veto powers - the US, Britain and France.
Al Jazeera's diplomatic editor, James Bays, reporting from the UN in New York said that the UN representatives pointed out that there are restrictions set by the Syrian government in getting aid to people.
"Only 14 international aid organisations are allowed in," he said.
Syria's UN Ambassador Bashar Ja'afari said the Syrian government was doing "everything possible to shoulder its responsibility and its duty to its people, to meet the humanitarian needs and the basic needs of its citizens."
UN aid chief Valerie Amos said the world was "not only watching the destruction of a country but also of its people".
She said 6.8m Syrians need urgent humanitarian assistance, including more than 4.2m internally displaced, and that almost half of those needing help were children.
The latest assessment by the World Food Programme was that four million people can no longer meet their basic food needs.