Hasbro, the US toymaker, yesterday filed a long-expected legal broadside against Scrabulous, an ersatz version of the company's Scrabble word game that sparked a sensation on Facebook when it launched on the social network last year.

The company, which owns the rights to Scrabble in the US and Canada, accused Rajat Agarwalla and Jayant Agarwalla, two Indian brothers who created Scrabulous in 2005, of committing "blatant infringement" of its intellectual property by copying Scrabble's rules, format and name.