SYDNEY, Oct 28 (Reuters) - Australia's Coles Group Ltd said first-quarter sales jumped 10.5% as coronavirus lockdowns boosted demand for home cooking supplies and forecast a strong holiday season due to a population unable to travel abroad.

The country's No. 2 supermarket chain has been one of the biggest beneficiaries of enforced social distancing during the quarter, particularly in the state of Victoria where a second wave outbreak kept people home until this week.

Coles' supermarket sales, its main earner, rose 9.7% in the three months to September from the same period a year earlier, while liquor store and convenience store sales showed double-digit growth, it said in a limited trading update on Wednesday.

It noted, however, that supermarket sales outside Victoria grew a slower 7.7% and "tapered off" toward the end of the quarter with restaurants and bars in the rest of Australia able to open on a limited basis.

It expects heightened demand over the upcoming December Christmas period due to restricted travel and after many Australians' plans were disrupted last year due to summer bushfires.

"There'll be a lot of ... entertainment gatherings going on. Until a vaccine is introduced there are more Australians in Australia than ever before and we expect that to be the case for at least six to 12 months," CEO Steven Cain said on a call with analysts.

Coles shares were up 2.3% by mid-session, outperforming a flat overall market. They have climbed 9% since late February compared to an 18% drop for an index of Australia's 20 largest companies.

Larger rival Woolworths Group Ltd, which reports on Nov. 4, has said in previous earnings updates that supermarket sales have surged during the pandemic but mandated closures or restricted trading have hurt sales at the pubs and hotels division it wants to spin off.

($1 = 1.4027 Australian dollars) (Reporting by Byron Kaye in Sydney and Nikhil Kurian Nainan and Rashmi Ashok in Bengaluru; Editing by Edwina Gibbs)