The poll is being held with Sri Lanka's President Mahinda Rajapakse under international pressure to allow a fair vote for the Provincial Council in the once strife-torn region which was a former stronghold for the Tamil Tiger separatist rebels.
The Tigers were crushed by a Sri Lankan military onslaught in 2009, which remains dogged by war crimes allegations, and the army maintains a heavy presence throughout the region of about a million people.
He asked for the army to be confined to their barracks for the election.
The Tamil Tigers, which held sway over a third of the country at their height, fought for a homeland for the ethnic Tamil population in Sri Lanka which is majority Sinhalese Buddhist.
Many Tamils complain they are treated as second-class citizens and face discrimination and Saturday's vote is seen as crucial in reducing ethnic tensions.