The Karnataka government had requested the CBI to take over the probe in the case.

The Central Bureau of Investigation or CBI has taken up investigation into alleged phone tapping of politicians during the term of the Congress-JD(S) government in Karnataka, officials said on Saturday.

The Karnataka government had requested the CBI to take over the probe in the case from the cyber crime wing of Bengaluru Police, they said.

The BJP government in the state had ordered a CBI enquiry on August 19.

"It has come to the notice of the government that there are apprehensions of phones of several ruling and opposition political leaders, their relatives and other government officials being intercepted in an illegal unauthorised unwarranted manner," the letter entrusting the probe to the CBI said.

The government asked the CBI to inquire into all such interceptions of "telephones of political leaders belonging to the ruling party and opposition parties as well as their associates, relatives and also of the government servants from August 01, 2018 till August 19, 2019".

It urged the agency to identify and investigate those involved in the interception.

The letter was forwarded to the CBI on August 30 by the Centre which was converted into an FIR against unidentified public servants and private persons on the same day.

Soon after taking over as chief minister, BS Yediyurappa had announced a CBI probe amid signs that the scandal was gaining political steam ever since disqualified JD(S) MLA AH Vishwanath, who served as JD(S) state president and turned rebel, accused the H D Kumaraswamy government of tapping phones and spying on more than 300 people, including him.

Congress leaders, including Siddaramaiah, M Mallikarjuna Kharge and home minister in the alliance government M B Patil, had sought a probe while another key party leader and former minister DK Shivakumar rejected the snooping charges and appeared to side with HD Kumaraswamy.

According to reports, phones of those close to Siddaramaiah, who was the coalition coordination committee chief then, too had come under the watch.

Several BJP leaders, including former chief minister Jagadish Shettar, have directly accused Kumaraswamy of being behind the episode to save his government which was then rocked by dissidence within.