The European Commission said it had received a number of complaints on Poland's allocation in 2013 of a frequency block from the 800MHz 'digital dividend band' to Sferia without a selection procedure, at no additional cost, and without coverage obligations.

"The Commission's preliminary view is that Sferia may have been awarded by the Polish authorities 800 MHz frequencies on more favourable terms than other operators and that, hence, the allocation may have amounted to state aid," the EU executive said in a statement.

(Reporting by Foo Yun Chee)