In Syria, activists said rebels completed their takeover of the northern city of Raqqa after seizing two key security buildings there. If confirmed, it would be the first major city to fall completely into rebel hands since Syria's conflict began nearly two years ago.
The U.N., meanwhile, said about 20 peacekeepers in a force that monitors the cease-fire between Israel and Syria in the Golan Heights were detained Wednesday by about 30 armed fighters. U.N. deputy spokesman Eduardo del Buey said the U.N. observers were stopped near an observation post which sustained damage and was evacuated last weekend following heavy combat.
In Geneva, the U.N. High Commissioner for Refugees, Antonio Guterres, said that the figure of 1 million refugees is based on reports from his agency's field offices in countries neighboring Syria that have provided safe haven for refugees escaping the 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 spiraling toward full-scale disaster," Guterres said. Syria's population is about 22 million.
In addition, several hundred thousand Syrians who have fled their country have not yet registered as refugees, suggesting the total number well exceeds 1 million, said Adrian Edwards, a spokesman for the U.N. refugee agency.
Syria's uprising began in March 2011 with protests against President Bashar Assad's authoritarian rule. When the government cracked down on demonstrators, the opposition took up arms and the conflict turned into a full-blown civil war. The U.N. estimates that more than 70,000 people have been killed.
The pace of refugees fleeing the battered country has picked up dramatically over the past three months.
In Lebanon, 19-year-old Bushra, a mother of two, became the millionth Syrian refugee registered in the region since the conflict began. Since fleeing the fighting in central city of Homs a few weeks ago, Bushra has lived in the Lebanon's restive city of Tripoli, squeezed into a room with 20 other people.
"Our life conditions are very bad, it is very expensive here (in Lebanon) and we cannot find any work," Bushra, who asked to be identified with her first name for fear of government reprisals, told reporters at a UNHCR registration center in Tripoli in northern Lebanon.
The U.N. refugee agency has registered more than 300,000 Syrians in Lebanon, although its representatives say many more Syrians are living in the country in dire need of basic aid.
Guterres said the number of refugees has swelled dramatically this year, with most pouring into Lebanon, Jordan, Turkey, Iraq and Egypt. More than 400,000 people have become refugees since Jan. 1, and often arrive in neighboring countries "traumatized, without possessions and having lost members of their families," he said.
Around half are children, the majority under age 11.
"We are doing everything we can to help, but the international humanitarian response capacity is dangerously stretched," he said. "This tragedy has to be stopped."
In Beirut, Panos Moumtzis, the UNHCR regional coordinator for Syrian refugees, said that 7,000 Syrians have been crossing into neighboring countries every day since the fighting escalated in December.
This has stretched the resources of states like Lebanon and Jordan and has made the refugee crisis one of the fastest deteriorating situations in decades, he said.
"When you stand at the border crossing, you see this human river flowing in, day and night," Moumtzis told The Associated Press after inspecting UNHCR's registration centers at border crossings in Lebanon.
He said the U.N. refugee agency badly needs money to help host countries cope and manage the refugee population, adding that of the $1 billion for aiding Syrian refugees in neighboring countries that was pledged at the Kuwait donor conference in January, only $200 million has come through.
"We are getting desperate," Moumtzis said, adding that the agency is able to provide Syrians fleeing violence with a bare minimum: a tent, a blanket, a sleeping mat, 2,000 calories of food and 20 liters of water a day.
"We are going hand to mouth, constantly trying to catch up in a crisis that is complex and dangerous because it has a potential to turn into a regional conflict," Moumtzis said.
Also Wednesday, the chief of the rebel army, Gen. Salim Idris, pleaded with the international community to provide anti-tank and anti-aircraft missiles, saying they are urgently needed to protect Syrian civilians against regime warplanes. Speaking in Brussels, Idris said the West must do more to help the rebels.
Britain signaled it is stepping up support for the rebels. Foreign Secretary William Hague said his country will provide armored vehicles, body armor and search-and-rescue equipment to Syria's opposition - while stopping short of arming the rebels.
Britain is broadening its technical assistance as a "necessary, proportionate and lawful response to a situation of extreme humanitarian suffering," Hague told the House of Commons. EU sanctions against Syria prevent the supply of arms to rebels, and the West has balked at intervening militarily in the conflict.
Fighting raged Wednesday in several parts of the country, especially in Raqqa where rebels overran two major pockets of regime resistance.
The Britain-based Syrian Observatory for Human Rights and other activists said rebels seized control of the Military Intelligence headquarters and another security building in Raqqa after three days of fighting, and freed scores of detainees inside.
The Observatory said the strategic city of 500,000 people on the Euphrates River is now completely under rebel control. The takeover would consolidate recent rebel gains in the towns along the river, which runs from Turkey to Iraq.
Rebels captured most of the city Monday, tearing down a giant statue of Assad's father and predecessor, Hafez Assad, as well as posters of the leader.
Syria's pro-government daily Al-Watan said "terrorists" - a term the regime uses for rebels - have occupied several government buildings in the city. It also confirmed reports that that the rebels captured Raqqa's governor, Hassan Jalali, and the head of the ruling Baath party's branch, Salman al-Salman.
The Observatory said earlier Wednesday that army reinforcements coming from the nearby town of Tabqa, also known as Thawra, clashed with rebels on the way to Raqqa. It said rebels are holding 300 soldiers and pro-government militiamen who were captured in the recent fighting.
Rising reported from Berlin. Associated Press writers Robert H. Reid in Berlin, Albert Aji in Damascus and Bassem Mroue and Karin Laub in Beirut and Edith M. Lederer at the United Nations contributed to this story.