PRESIDENT Abdullah Gul has ordered state auditors to assess Turkey's ability to combat corruption, including in the construction sector, amid a fraud investigation that has implicated senior elected officials.

Mr Gul also said he had instructed the State Supervisory Council to examine regulations governing the tapping of communications.

In one of the biggest challenges of his 11 years in office, Prime Minister Tayyip Erdogan is battling a series of allegations that he, members of his family and senior government officials took bribes and engaged in other improprieties.

Mr Erdogan, a popular leader whose party has been elected three times since 2002, has accused a United States-based Islamic cleric, Fethullah Gulen, and his followers of concocting the charges to sway voters ahead of a local election this month.

Mr Gul, a co-founder of Mr Erdogan's centre-right AK Party, has come under pressure to speak out on the corruption scandals.