Former Karnataka chief minister HD Kumaraswamy on Saturday begins a fast-unto-death for a probe to determine if his family's Rs1,500 crore assets were legally acquired or not.

Kumaraswamy is the son of former prime minister HD Deve Gowda, who was contractor for civil works for the state's public works department (PWD) before joining politics in 1953 as Congress party member.

The Gowda family of four sons and two daughters is accused by the ruling Bharatiya Janata Party (BJP) of "amassing assets now valued at Rs1,500 crore by illegal means".

The assets, listed in a booklet made public by BJP on June 28, include land, commercial and residential properties and several companies run by the family members -- mainly by the sons and daughters-in-law.

The booklet, "Amassing wealth by corrupt practices: A tell-tale story of HD Kumaraswamy and family", was released to counter his charges against chief minister BS Yeddyurappa.

Gowda, who heads the Janata Dal-Secular, and Kumaraswamy, JD(S) state president, have not contested the details of the properties listed in the booklet. They are only saying that "all these are legally acquired".

Immediately after the release of the booklet, the father-son combine dared Yeddyurappa to seek a Central Bureau of Investigation (CBI) probe to find out whether the assets were illegally acquired.

On June 29, Kumaraswamy announced that he was giving one week to Yeddyurappa to order the probe and will go on a "fast-unto-death" from July 9.

Yeddyurappa Thursday ruled out a CBI probe. He told reporters in Mysore, about 130 km from Bangalore, that the state government officials were already probing how the assets were acquired and hence CBI was not needed.

Kumaraswamy, 52, was a Kannada film distributor and producer before launching his political career.

He is now a JD(S) Lok Sabha member. His wife, Anitha, is member of the legislative assembly and an entrepreneur. She runs a Kannada TV channel and the couple has one son.

Besides Kumaraswamy, the other Gowda son in politics is HD Revanna, who is a JD(S) leader in the state assembly.

The other two sons are not into politics. The eldest, HD Balakrishne Gowda, was a Karnataka government official while the youngest -- HD Ramesh -- is a doctor.

Since the father and two sons hold top positions in the JD(S), opponents mock it as "thande-makkala paksha" (father and sons party).

Kumaraswamy wanted to fast in front of the state secretariat building. However, he has changed the venue after Yeddyurappa said "no one, however high, will be allowed to stage protest in front of Vidhana Soudha".

Yeddyurappa also ruled out persuading Kumaraswamy to drop his fast.

It will be a tense period for the state, particularly tech-hub Bangalore, if Kumaraswamy sticks to his plan and fast continues for a few days, affecting his health.

He has said that he is suffering from "sugar complaint and heart-related ailments". Though doctors had advised him against fast, he will go ahead as otherwise "people will believe that we have something to hide", Kumaraswamy has said.