JOHANNESBURG, Jan 30 (Reuters) - South Africa's biggest supermarket group Shoprite reported on Tuesday a 13.9% jump in half-year sales, supported by a record Black Friday and festive season as both cash-strapped shoppers and upmarket consumers went after food deals.

The retailer, with over 2,900 stores across Africa, said group sales for the six months ended Dec. 31 rose to 121.1 billion rand ($6.44 billion). Second quarter sales, which include November and the Christmas holiday period, rose by 14.6%.

Cash strapped shoppers, hit by high interest rates and inflation, are spending less on discretionary items like clothes and shoes, spending their money on food and essentials.

($1 = 18.7998 rand) (Reporting by Nqobile Dludla; Editing by Christian Schmollinger)