[JURIST] Over 50 percent of eligible voters in Montenegro [CIA backgrounder] have already cast their ballots in Sunday's referendum on independence from Serbia, according to ballot observers from the Center for Democratic Transition (CDT) [official website, with vote updates], meeting the threshold requirement to validate the referendum [BBC Q/A]. Voters have until 9 PM to vote on whether the small republic will become Europe's newest nation. A majority of over 55 percent of those who cast votes must elect in favor of independence for the resolution to pass.

The 55 percent majority requirement was set by the European Union and has been criticized [JURIST report] by some Montenegrin leaders as "undemocratic." Nonetheless, the referendum is expected to pass, as polls have shown that over 55 percent of Montenegrins support independence despite the resistance of Serbian nationalists within Montenegro. If Sunday's referendum produces the 55 percent majority, the Montenegro Parliament [official website] will incorporate the referendum into a bill during a special session scheduled for Wednesday. Reuters has more. A Montenegrin split from Serbia would mark the final stage in the collapse of the post-World War II Balkan state of Yugoslavia, leaving Serbia isolated after the previous breakaways of Bosnia and Herzegovina, Croatia, Slovenia and Macedonia. BBC News has additional coverage.

4:23 PM ET – The BBC is reporting that Montenegro has narrowly voted for independence from Serbia, according to initial projections. Radio Televizija Crne Gore provides the latest coverage.

6:35 PM ET – Montenegro television is unofficially reporting a 55.3% majority for independence, just over the 55% required. Visit the official referendum website. Official results from the referendum are expected Monday. Reuters has more.