The probe follows a complaint that Alphabet Inc's Google unit had "abused its dominant position and made the efforts of other companies difficult", the authority said.

The investigation will include companies Google Reklamcilik ve Pazarlama, Google International LLC, Google LLC, Google Ireland Limited and Alphabet Inc., it said.

Calls by Reuters to Google Reklamcilik ve Pazarlama, Alphabet's local unit, were not answered on Monday.

In September, the authority fined Google some 93 million Turkish lira (£13.5 million) for violating competition law with its mobile software sales.

(Reporting by Ezgi Erkoyun; Writing by Tuvan Gumrukcu; Editing by David Dolan and Catherine Evans)