A million Syrians have fled their country since a deadly civil conflict erupted two years ago, the UN refugee agency says.
The UN High Commissioner for Refugees (UNHCR) said on Wednesday thousands more continued to flee Syria where an uprising began in March 2011 and has since escalated into a civil war.
"With a million people in flight, millions more displaced internally, and thousands of people continuing to cross the border every day, Syria is spiralling towards full-scale disaster," Antonio Guterres, the UN High Commissioner for Refugees, said in a statement.
"We are doing everything we can to help, but the international humanitarian response capacity is dangerously stretched. This tragedy has to be stopped."
The UNHCR said the one million figure comprised both registered refugees and those awaiting registration.
The count was based on fresh data received from its offices in the Middle East, the UNHCR said.
The agency previously had estimated that numbers would reach 1.1 million by June but said that it would adjust that figure.
Al Jazeera's Nisreen El Shamayleh, reporting from the Kilis refugee camp in Turkey, said the host country has paid a "very heavy" price to host the Syrians who fled their country.
Turkey has so far spent more than $700m on refugees since the beginning of the conflict, she said.
Of that amount Turkey has received $89m in foreign aid.
The are more than 186,000 registered Syrian refugees in Turkey, with over 100,000 staying elsewhere, and 40,000 more stranded along the border between Syria and Turkey, our correspondent said.
The exodus has intensified this year, the UNHCR said, with 400,000 Syrians fleeing their country since January 1.
Only a year ago, the UN agency had only registered 33,000 refugees.
Forces loyal to Bashar al-Assad, the Syrian president, have been battling armed factions that have seized part of the country's north in a conflict that the UN estimates has killed 70,000 people.
Most of the anti-Assad rebels are Sunni Muslims, while the ruling clan and many of its most fervent supporters are from the Alawite minority, an offshoot of the Shia sect.
The UN said the latest refugees "arrive traumatised, without possessions and having lost members of their families". Around half of the refugees are children, the majority under the age of eleven.
The refugees have fled primarily to Lebanon, Jordan, Turkey, Iraq and Egypt, but increasingly they are trying to reach North Africa and Europe, the UNHCR said.
In-depth coverage of escalating violence across Syria
"This number translates into one million people who are dependent on the generosity of host countries, the response of humanitarian agencies and the financial support of governments and individuals," said Guterres.
He underlined the impact of the numbers, with Lebanon's population having increased by as much as 10 percent and Jordan's energy, water, health and education services being strained to the limit.
Iraq, already struggling with a million internally displaced people, has received over 100,000 Syrian refugees in the past year.
"These countries should not only be recognised for their unstinting commitment to keeping their borders open for Syrian refugees, they should be massively supported as well," said Guterres.
The UNHCR chief is due to travel to the region later this week to visit the agency's operations in Turkey, Jordan, and Lebanon.