McDonald’s, the fast-food giant, has reported a 2.3% rise in sales across its European stores in May, compared with a 5.7% increase a year ago. McDonald’s said the sales growth was driven by strong performances in the UK, France and Russia, boosted by limited time events, such as the Great Tastes of America campaign. However, sales in the region were offset by a weaker performance in Germany, which was impacted by the recent food contamination problems. Andy Barish, analyst at Jefferies & Co, said the results showed the potential impact of gas prices and economic uneasiness in Europe. Sales in the Asia, Africa and Middle East region climbed 4.3% for the month year-on-year and sales in its homeland, the US, were 2.4% ahead. Global comparable sales were up 3.1% in May, a slowdown on the 4.8% reported during the same period in 2010. At the same time, the fast food chain said it plans to become the first company of its type to sell fish in Europe that’s been certified as sustainable by the Marine Stewardship Council (MSC). The group will start selling MSC-certified white fish, including in its Filet-O-Fish sandwiches, at 7,000 restaurants in 39 European countries from October.