CBI raids conducted at the residence of P Chidambaran and Karti

Official sources in Delhi said the searches were spread across Mumbai, Delhi, Chennai, and Gurugram.

The raids are also taking place at the Nungambakkam residence of P Chidambaram in Chennai, a senior police official said in Chennai.

Unconfirmed reports said the raids were also on at Karaikudi, the hometown of Chidambaram.

The agency had recently registered a case regarding Foreign Investment Promotion Board (FIPB) clearance given to INX Media, which was once owned by Peter Mukerjea, in which it is alleged that favours were given when P Chidambaram was the finance minister.

Asked about the raids, the former union minister said, "You should have called your CBI friends.......Should I stop writing ? (against the government)."

"I mean...(this is) absolute nonsense," Chidambaram told PTI adding he was not in Chennai.

Chidambaram, a staunch critic of the Narendra Modi-led BJP regime, has said in the past that his voice against the Centre cannot be silenced by launching cases against him or his son Karti, also a Congress leader.