The Latest on Colombia's referendum on an agreement to end a half-century of armed conflict (all times local):

8:15 a.m.

Polls have opened in Colombia's referendum where voters will be asked whether to endorse or reject a historic peace deal with the country's largest rebel movement.

Authorities are urging Colombians to vote early, though heavy rainfall from the offshore passage of Hurricane Matthew is expected to dampen turnout.

In Plaza Bolivar, where President Juan Manuel Santos is voting, there were long lines of voters standing with umbrellas waiting to cast ballots.

At least 13 percent of the electorate, or around 4.5 million voters, must ratify the accord signed Sept 26 in order for implementation to begin. Polls show the "yes" vote favored by an almost two-to-one margin.