(CNN) -- The United Nations on Friday made its largest appeal ever -- for more than $5 billion -- for relief aid to Syrians across the country.
"Syria as a civilization is unraveling, with as many as half of its citizens in need of urgent help as a result of this savage conflict," said Antonio Guterres, the world body's high commissioner for refugees, who announced the goal in Geneva. "The funds we are appealing for are a matter of survival for suffering Syrians, and they are essential for neighboring countries that are hosting refugees."
More than 1.6 million Syrians have fled the country since the conflict began in March 2011; another 4.25 million are estimated to have been displaced inside it.
UNHCR noted that it had appealed in December for $1 billion, but increased the figure after the number of refugees exceeded predictions.
The announcement came as the U.N. Office for the Coordination of Humanitarian Affairs predicted that 3.45 million inside Syria could have crossed its borders by the end of the year and another 6.8 million people remaining inside Syria will need aid.
That's nearly half of the nation, which has a population of 22.5 million.
On Thursday, the European Union said it would contribute as much as $530 million to aid Syrians by year's end.
Two days after Syrian government forces seized control of the strategically important city of Qusayr from rebel forces it describes as "terrorists," the army sought to restore security and stability to surrounding villages, the state-run Syrian Arab News Agency reported Friday.
"An official source told SANA reporter that units of our armed forces are continuing their missions in pursuing the terrorists' remnants and inspecting operations," it said.
The U.N. Security Council urged on Friday that Syrian authorities protect civilians and allow humanitarian access to the town.
UNHCR said this week that it had received reports that up to 1,500 wounded civilians were trapped in the town.
At least 52 people -- including three women and four children and one under torture -- were killed Friday nationwide, the rebel Local Coordination Committees of Syria said.
In addition, two French journalists working for Europe1 are missing in Syria, the French radio station said Friday, prompting fears that they may have been kidnapped.
Reporter Didier Francois and photographer Edouard Elias were on their way to the northwestern city of Aleppo when they went missing, the radio station said.
Lebanon's official National News Agency reported that one person was killed and several were wounded in clashes in Tripoli.
Deteriorating security conditions near the Golan Heights headquarters for U.N. peacekeepers in the region prompted Austria to say Thursday that it will pull out its 370 troops, more than a third of the force assigned to help keep Israel and Syria at bay.
The announcement came amid fighting over the Quneitra crossing, Syria's only access point to the Golan Heights. Rebel forces first captured but then lost control of the crossing in heavy fighting.
On Friday, Russian President Vladimir Putin said Moscow was prepared to replace them, Russia's Itar-Tass news agency reported.
The developments come amid longstanding concerns that the conflict could expand to other parts of the region.
U.N. spokeswoman Josephine Guerrero said Filipino and Indian peacekeepers will remain in the region to enforce the peace deal between Israel and Syria reached in 1974, nearly seven years after Israel first captured Quneitra in the Six-Day War. Syria retook it in 1973.
Quneitra is important to the Syrian regime because it represents former President Hafez al-Assad's attempt to liberate Israeli-occupied territory.
CNN's Hamdi Alkhshali contributed to this report.