Hundreds of festive southern Sudanese lined up outside a polling station in Cairo on Sunday to vote in a referendum that may lead to an independent southern Sudan.

Men and women danced and sang in the southern Cairo neighbourhood of Maadi Gadida, one of three polling stations set up in the Egyptian capital for 3,349 Sudanese who registered to vote in the historic referendum.

"This is a historic day, we will finally decide for ourselves and stop the disaster that has lasted 50 years," said Otogo Lee, one of the voters.

A man waving the southern Sudanese flag encouraged the crowd with chants of "freedom."

Wanilokon Diana Wislin, a housemaid, said she arrived early in the morning. "It's a happy day, we're all here for a new future. I will go home as soon as independence is declared," she said.

An estimated 7,000 southern Sudanese live in Egypt.

Those who registered have a week to vote, said Mary Isaac, the electoral commission's representative in Egypt.

About four million southerners in Sudan and abroad are eligible to vote in the referendum, which was a key plank of a 2005 peace treaty that ended a 22-year civil war between the Muslim north and mostly Christian south.

Final results are expected by February 15.