ISTANBUL, March 11 (Reuters) - Turkey's competition authority has launched an investigation into 65 companies in the auditing and financial advisory sector, including global accounting firms, it said on Wednesday.

The authority said the probe includes the Turkish units of the so-called Big Four: KPMG, PwC, Deloitte and EY.

In a statement, the authority said the probe aims to determine whether firms and professional organisations in the sector coordinated on service fees or engaged in anti-competitive practices in the labour market.

The authority said it is examining whether companies shared service prices or client portfolios in ways that may have violated competition, whether they took decisions that could block market entry or distort competition, and whether there shared information that negatively affected employee rights and wages.