Russia's X5 Retail posts 21 pct rise in Q4 sales, inflation boosts

* Sales growth helped by higher food inflation

* Budget Pyaterochka stores attract more customers

* FY sales up 18.6 pct, in line with guidance (Adds details)

MOSCOW, Jan 21 (Reuters) - Russia's second-biggest grocery chain X5 Retail Group said on Wednesday higher food inflation had increased the average customer spend in its stores as it reported a 20.8 percent rise in sales in the fourth quarter.

Its low-cost Pyaterochka stores attracted more shoppers but its supermarkets and hypermarkets saw lower numbers because of an economic slowdown, X5 said, deepened by Western sanctions over Russia's role in Ukraine and weak oil prices.

X5 said sales in October-December amounted to 180.9 billion roubles ($2.8 billion), up from around 150 billion a year ago, as it added around 940 stores during 2014, while like-for-like sales grew 11.6 percent, year-on-year.

Like-for-like sales growth was driven by a 12 percent jump in the average bill, fuelled by inflation which helped offset a 0.4 percent fall in customer traffic.

For the full year 2014, X5 reported an 18.6 percent increase in sales to 631.9 billion roubles, in line with its forecast for 17-19 percent growth. Like-for-like sales grew 9.8 percent.

X5, majority owned by billionaire Mikhail Fridman, has been working on turning around its business after a strategy change in 2010 aimed at growing without acquisitions. It ceded its No.1 position by sales to low-cost rival Magnit and has suffered from multiple management reshuffles.

Magnit earlier posted a 32 percent jump in 2014 sales to 763 billion roubles.

($1 = 65.2500 roubles) (Reporting by Maria Kiselyova; editing by Elizabeth Piper)