BRUSSELS, Jan 20 (Reuters) - U.S. distributor Valve Corp, owner of the world's largest video game distribution platform Steam, and 5 video game publishers received a 7.8-million-euro ($9.45 million) EU antitrust fine on Wednesday for blocking cross-border sales in Europe.

The penalty followed a four-year investigation, as part of the European Commission's crackdown on cross-border curbs on online trade in the bloc.

Valve did not admit wrongdoing and was fined 1.66 million euros. Fines for the five video game publishers - Bandai Namco , Capcom, Focus Home, Koch Media, part of Embracer Group AB, and ZeniMax - were reduced by 10%-15% after they admitted wrongdoing.

The Commission, the EU executive, said the companies' practices prevented European consumers from shopping around in a European market worth more than 17 billion euros.

"Today's sanctions against the 'geo-blocking' practices of Valve and five PC video game publishers serve as a reminder that under EU competition law, companies are prohibited from contractually restricting cross-border sales," EU Competition Commissioner Margrethe Vestager said in a statement.

The EU competition enforcer said Valve and each publisher bilaterally agreed to geo-block certain PC video games from outside a specific territory, affecting some 100 video games.

($1 = 0.8251 euros) (Reporting by Foo Yun Chee; editing by Barbara Lewis)