The EU launched an in-depth probe Monday into alleged sweetheart tax deals between French gas group Engie and Luxembourg, taking on a major European multinational after similar high-profile investigations into US giants.

"The Commission has concerns that several tax rulings issued by Luxembourg may have given GDF Suez (now Engie) an unfair advantage over other companies, in breach of EU state aid rules," the European Union's executive arm said in a statement.

The probe comes days after the Commission angered Washington with a ruling that US tech icon Apple had received favourable tax terms that amounted to state aid and ordered it to repay 13 billion euros ($14.5 billion) in back-taxes in Ireland.