BRUSSELS, Sept 25 (Reuters) - The European Commission has opened an investigation into possible anticompetitive practices by Germany's SAP SAPG.DE, Europe's largest software maker, related to its popular business management software.

SAP shares fell 2% on the news.

The commission said SAP is seen to have distorted competition in the market for maintenance and support services for its Enterprise Resource Planning software.

"Thousands of companies across Europe use SAP's software to run their business, as well as its related maintenance and support services," European Commission Vice President Teresa Ribera said in a statement on Thursday.

"We are concerned that SAP may have restricted competition in this crucial aftermarket, by making it harder for rivals to compete, leaving European customers with fewer choices and higher costs," she added.

SAP said it would cooperate with the commission, adding that it believed its policies and actions were "fully in line with competition rules."

Reuters reported on Monday that SAP had offered concessions to address EU antitrust concerns over its business practices, seeking to avert a probe and the risk of a fine of as much as 10% of its annual global sales.