HONG KONG (AFP) - About 10,000 Australians are expected to cast their vote in their nation's federal elections in Hong Kong, one of the country's biggest overseas polling stations.

A record 14.71 million Australians are registered for the upcoming election, when they will choose between incumbent Prime Minister Kevin Rudd's Labor party, the conservative opposition of Tony Abbott or more than 50 other minor parties.

Voting is compulsory in the country but not for Australians living overseas.

"If you are not in Australia on polling day it is not compulsory, but we still find that Australians are keen to have their say," Australian consulate spokesman Gavin McDougall told AFP in the southern Chinese city.

Australians, which number 80,000 to 90,000 in Hong Kong, started voting in the city last Monday and can place their ballots until election day on September 7.

Mr Kevin Rudd, who is lagging behind in polls, has a large election billboard with a picture of his smiling face in downtown Hong Kong.

The city is the second largest polling centre overseas. During the last election, more than 16,000 people - tourists and expatriates - cast their ballots at the Australian embassy in London, and around 7,800 in Hong Kong.