The number of refugees from the Syria conflict now tops three million, the UN said Friday, as US President Barack Obama admitted he has no strategy to tackle advancing jihadists.
In Geneva, UN refugee agency chief Antonio Guterres said Syria had become the "biggest humanitarian emergency of our era" after a million people joined the exodus in the past year alone.
They have fled the war-wracked country where Islamic State (IS) jihadists have sown panic with atrocities and executions, including of scores of Syrian soldiers and a US journalist this month alone.
The scale of the crisis facing the international community deepened after rival Islamists led by Al-Qaeda's Syria affiliate, Al-Nusra Front, seized 43 Fijian UN peacekeepers on the Golan Heights.
"The latest information we have is that they are safe and I can say now that the negotiations for their release have already begun," Fiji's Prime Minister Voreqe Bainimarama said in a statement.
The militants also surrounded 75 Filipino peacekeepers, sparking a tense standoff for the UN mission that has monitored a Syrian-Israeli armistice on the strategic plateau for decades.
Dampening prospects of imminent air strikes in Syria, Obama said he was still developing a comprehensive plan to defeat IS, which has overrun large swathes of neighbours Iraq and Syria.
"We don't have a strategy yet," Obama said, adding however that he was sending Secretary of State John Kerry to the Middle East to build regional support against IS.
The Syria war has killed some 191,000 people since March 2011 but has taken on a new dimension as IS unleashed a brutality that has shocked the world.
Britain announced Friday that it has raised the terror level to "severe" because of concern that jihadists in Syria and Iraq were planning attacks on the West.
British Prime Minister David Cameron told reporters there was "no doubt in my mind" that IS had its sights set on targets in Europe.
The White House spokesman said the United States had no plans to follow suit.
- 'Message in blood' -
Washington has launched air strikes in Iraq that have helped Kurdish forces claw back some territory lost to a renewed jihadist offensive earlier this month.
This has infuriated the jihadists who posted grisly video footage Thursday of their execution of a Kurdish fighter.
The video also shows other captive Kurds warning that they risk the same fate if such cooperation continues, the SITE Intelligence Group monitoring service said.
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The footage follows a jihadist video showing scores of bodies in the desert that IS boasted were Syrian soldiers it captured and killed.
The jihadists have also carried out a spate of executions of civilians from religious minorities in northern Iraq.
On Friday, Iraqi aircraft struck jihadists besieging the Shiite Turkmen town of Amerli for more than two months, as government forces readied an offensive, officers said.
Amerli residents are in grave danger both because of their Shiite faith, which jihadists consider heresy, and their resistance to the militants, which has drawn harsh retribution elsewhere.
"Whole communities that had lived for generations in northern Iraq are being forced to flee or face death just for their religious beliefs," UN chief Ban Ki-moon said Friday.
His comment came as the International Organisation for Migration said that over 1.6 million Iraqis have been displaced this year, more than 850,000 this month alone.
"Many of their loved ones were killed or abducted by IS forces. Groups of people were reportedly forced by IS to jump off mountain cliffs, while others were taken away to an uncertain fate," said the IOM emergency coordinator for Iraq, Brian Kelly.
A UN-mandated probe has charged that public executions, amputations, lashings and mock crucifixions have become commonplace in jihadist-controlled areas of Syria.
- UN peacekeepers held -
As Fiji's premier announced that negotiations were under way to free 43 of his countrymen captured in Syria, Manila said its citizens besieged by rebels were ready to use "deadly force" to defend themselves.
The UN peacekeepers from Fiji were forced to surrender their weapons and were taken hostage, but the 75 Filipino blue helmets "held their ground" and refused to disarm, the Philippine defence department said.
The UN Security Council demanded the "unconditional and immediate release" of the peacekeepers.
Twice last year peacekeepers were detained before being released.
Meanwhile, Hollywood star and goodwill ambassador for the UN refugee agency Angelina Jolie made a plea for the end of Syria's three-and-a-half war.
"Three million refugees is not just another statistic. It is a searing indictment of our collective failure to end the war in Syria," she said.
On the ground, regime forces blasted Damascus's eastern district of Jubar on Friday as they sought to retake the strategic rebel-held sector.