Chennai, Dec 20 (IANS) Calling the summoning of former communications minister A. Raja by the Central Bureau of Investigation (CBI) as a "routine" affair, Tamil Nadu Chief Minister M. Karunanidhi said Monday that the CBI probe into Raja's affairs won't hit Congress-DMK ties.

"It is strong. You cannot cut it," the DMK chief said, when reporters asked him about the future of his party's alliance with the Congress. The two parties are allies in Tamil Nadu, and the DMK is a key member of the Congress-led United Progressive Alliance (UPA) government.

Karunanidhi said: "The CBI notice (to Raja over the spectrum allocation scandal) is a rotuine procedure, and Raja will reply to that."

The chief minister, however, promised action against Raja if he was proved guilty of selling second generation spectrum at below the market price, causing huge losses to the exchequer.

Did he view the CBI raids on Raja's residences as an insult to the DMK party, he said: "We do not consider it as an insult. The self-respect movement grew facing several insults."

The CBI has searched Raja's residences in New Delhi and in Perambalur in Tamil Nadu as well as the homes and business premises of his relatives and other associates.

Also raided by the CBI were a host of people associated with Raja, including corporate lobbyist Niira Radia and an NGO linked to DMK MP and Tamil Nadu Chief Minister M. Karunanidhi's daughter Kanimozhi.

Raja has denied charges of wrongdoing.