PODGORICA, Serbia-Montenegro (CNN) -- Voters in Montenegro decided narrowly to sever the country's union with Serbia, a move that would break up the last two pieces of the former Yugoslavia, unofficial poll returns from Sunday's referendum indicated. The election watchdog group CEMI said late Sunday that 55.5 percent of the more than 410,000 voters who cast ballots supported independence -- just over the 55 percent required for the question to pass. "I'm sure that tonight a democratic Montenegro will be celebrated," said Prime Minister Milo Djukanovic, whose Democratic Party of Socialists had pushed for Montenegro's full independence. Opposition spokesman Predrag...