As many as 700 people might have drowned overnight in the Mediterranean when their boat capsized during a desperate attempt to reach Europe, officials said Sunday, deepening a crisis that has shaken politicians as they struggle to cope with the disaster unfolding off Europe’s southern coastlines. Officials with the United Nations refugee agency, UNHCR, said on Sunday they believed only 28 passengers had survived the capsizing in the Strait of Sicily near the coast of Libya.