More than four million people inside Syria are in desperate need of aid, up sharply from 2.5 million in September, the United Nations said Tuesday, urging a rapid political solution to the crisis that has claimed at least 70,000 lives.
"We are watching a humanitarian tragedy unfold before our eyes," Valerie Amos, the UN under-secretary-general for humanitarian affairs and emergency relief coordinator, told reporters in Geneva.
Speaking after the seventh Syrian Humanitarian Forum bringing together different UN aid providers, she said the meeting had been heavily focused on "securing access to the millions of Syrians who desperately need help".
She said access was especially difficult in the opposition-held north, lamenting that the regime in Damascus was continuing to block UN agencies from bringing aid across the border from Turkey, forcing them to carry it across the battle lines instead.
"I have spoken to the government on a number of occasions about allowing us to bring in supplies across that border," Amos said, adding: "My last conversation with them was yesterday. The answer remains no."
A graphic from her office showed how the need for humanitarian aid has spiralled since March 2012, when some one million people were listed, to 2.5 million last September and four million by January.
"We consider these fairly conservative figures, and we are aware that there are probably a lot more people," Jens Laerke, spokesman of the UN Office for the Coordination of Humanitarian Affairs (OCHA), told AFP.
According to numbers provided by the US mission in Geneva, in six northern governorates alone -- of a total 14 in Syria -- some 1.1 million people have been displaced and more than three million are in need of food and health assistance.
Amos described the situation in the war-torn country as "devastating," lamenting that even though all the UN agencies working to help Syrians in need have dramatically scaled up their efforts, "we are not reaching enough of those who require our help."
"On my fourth visit to Damascus in January ... I have seen firsthand the destruction of lives and infrastructure and the erosion of basic social services like health and education," she said.
The crisis "requires a political solution," she said, adding: "The key tragedy here is that the international community has not found a political solution to this crisis."
Amos said that "because we don't have agreement around the UN Security Council table, (what) started off as a political crisis ... has become a major humanitarian and human rights crisis."
The United Nations says at least 70,000 people have been killed in the near two-year conflict, while some 2.5 million have been displaced by the fighting but remain in Syria.
Earlier Tuesday, the UN refugee agency said the number of Syrians who have fled their conflict-ravaged homeland has now topped 850,000.
Amos said more than 250,000 had fled since mid-December, adding: "These numbers are not sustainable."
Only a year ago, the United Nations said 33,000 Syrians had fled the conflict which erupted in March 2011 as the regime of President Bashar al-Assad launched a bloody crackdown on protests.
The United Nations has warned that refugee numbers could reach 1.1 million within months in what has become an increasingly radicalised civil war in the nation of almost 21 million.
Around 97 percent of the refugees have fled to neighbouring Lebanon, Jordan, Turkey and Iraq, Amos said.
She said Tuesday that the forum was working to ensure that more than $1.5 billion (1.1 million euros) pledged at a Kuwait donor conference for Syria last month be turned "into commitments so we can scale up our efforts on the ground".
OCHA meanwhile said it had received only about 20 percent of the $519 million requested by the UN agencies for their operations through June.