SYDNEY, July 7 (Reuters) - A two-week COVID-19 lockdown in Australia"s largest city of Sydney will be extended for another week in a bid to contain an outbreak of the highly infectious Delta virus variant, local media reported on Wednesday. The city, home to a fifth of Australia"s 25 million people, is fighting its worst outbreak of the year so far, with total cases reaching more than 330 since the first case was detected three weeks ago. New South Wales (NSW) state authorities imposed a hard lockdown on June 26 to get on top of the Delta strain. The stay-home orders were scheduled to end Friday, but will now end on July 16, media reports said. The office of the NSW state premier did not immediately respond to a request seeking comment. Existing restrictions, including mandatory masks indoors and in public transport, will remain for another week and schools in Sydney will move to remote learning when they end their winter break, the Sydney Morning Herald said in a report. Officials have said the lockdown has been effective as the tough restrictions limited daily cases to tens rather than hundreds, but the fast moving Delta variant in a country that has been slow to vaccinate alarmed officials. NSW is scheduled to report its daily COVID-19 numbers at 11 a.m. (0100 GMT). Lockdowns, swift contact tracing and a high community compliance with social distancing rules have helped Australia suppress past outbreaks and keep its COVID-19 numbers relatively low, with just over 30,800 COVID-19 cases and 910 deaths.