Myanmar is holding by-elections that are being seen as a key step in the country’s road to democracy.
It is the first time international observers will monitor polls in the former Burma.
A civilian government took office one year ago after five decades of military rule.
The speed of its reforms, including releasing political prisoners, has surprised some in the West.
The US and the EU could ease sanctions if this vote is free and fair.
Nobel Laureate Aung San Suu Kyi is contesting a seat in the parliament’s lower house.
She was freed from 15 years of house arrest in November 2010.
Her National League for Democracy boycotted that month’s general election on the grounds it was rigged.