MEXICO CITY, Feb 25 (Reuters) - Mexico's second-biggest retailer, Organizacion Soriana, on Monday reported its fourth-quarter profit fell 8.7 percent, hurt by a rise in costs. The supermarket chain said quarterly profit slipped to 1.106 billion pesos ($86 million) from 1.212 billion pesos in the October-December period in 2011. Sales costs and general costs both increased 6 percent from the year-earlier quarter, offsetting a 5 percent rise in quarterly revenue to 29.206 billion pesos from 27.767 billion pesos a year earlier. Soriana, which competes with retail giant Wal-Mart de Mexico, said it opened 50 new stores in 2012 to end the year with 606 supermarkets and 212 convenience stores. The company plans to open about 60 new stores in 2013, executives told analysts on a call. Soriana expects same-store sales - that is, revenue from stores open at least a year - to rise between 4 and 5 percent in 2013, executives said. Shares in Soriana were down 0.88 percent at 47.15 in afternoon trading.