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. Access to UN aid is especially difficult in the opposition-held north, given 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.

The need for humanitarian aid has spiraled since March 2012, when some one million people were listed, to 2.5 million last September and four million by January. 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.

The United Nations has warned that refugee numbers could reach 1.1 million within months in what has become an increasingly radicalized civil war in the nation of almost 21 million. Around 97 percent of the refugees have fled to neighboring Lebanon, Jordan, Turkey and Iraq.