(ShareCast News) - Sainsbury's third quarter like-for-like grocery sales were surprisingly positive and group revenue was further lifted by recently acquired Argos as online sales proved a crucial factor over the key festive period.Total group sales for the 15 weeks to 7 January rose 0.8%, with group LFL sales up 1.0% as weak LFL growth from the supermarkets business of 0.1% was offset by a 4% gain from Argos.Having fallen 1% in the first half of the year, many analysts had expected the supermarket business to endure a decline in LFL sales, but managed a small rise thanks to an increase in total volumes but with LFL volumes flat.Chief executive Mike Coupe said Sainsbury's had a record Christmas week, with over £1bn of sales across the group.The online groceries business grew by over 9% and along with the 6%-plus growth from the convenience store channel were key drivers, with online sales contributing a 18% of total group sales in the quarter."Clothing and general merchandise also had a very strong quarter, with clothing sales up 10%t and general merchandise up 3%," Coupe said, adding that Argos saw spurts of growth from Black Friday and the Christmas trading period.** More to follow **