ISTANBUL, Oct 22 (Reuters) - The Turkish communications watchdog has started a preliminary inquiry into an all-networks tariff offered by Turk Telekom's mobile subsidiary Avea, the regulator and the operator said on Thursday.
The inquiry would determine whether an investigation should be opened into Avea, number three in the Turkish mobile market, Turk Telecom said.
On Wednesday the watchdog launched a probe against the country's biggest mobile phone company Turkcell for applying fees in excess of the limits set by the watchdog.
Turkcell will have to repay the excess fees it collected from its subscribers within one month at the latest, the watchdog said.
Shares in Turk Telekom traded up 2.55 percent at 4.82 lira by 1300 GMT, outperforming the ISE index of leading Istanbul shares which slipped 0.76 percent. An Istanbul-based trader said the shares were benefiting from a resurgent interest in defensive stocks.
Turkcell by contrast traded down 1.9 percent at 10.40 lira.
The trader said any potential fine against Turk Telekom relating to Avea pricing was not seen as having a material impact, whereas the regulatory risk associated with Turkcell had curbed appetite.
Turkey has a fiercely competitive mobile phone market, and the three major operators have long been embroiled in a price war. The regulator has also frequently intervened in pricing. (Reporting by Alexandra Hudson; Editing by Jon Loades-Carter)