MUMBAI: Suspecting tax evasion of at least Rs 5,000-6,000 crore, regulator Sebi has clamped down on a large number of organised syndicates who had set up 'shops' to convert black money into legitimate-looking funds through the stock market platform.While more than 900 entities have been banned from capital markets by the Securities and Exchange Board of India (Sebi), it has also referred these cases to the Income Tax Department for further investigations."We have banned more than 900 entities and my guess is that the tax avoidance that has happened in these cases is more than Rs 5000-6,000 crore," Sebi Chairman U K Sinha said."We have given all the details to the CBDT ( Central Board of Direct Taxes ) and we have told them that they should probe them," Sinha told PTI in an interview here.Talking about the menace of money laundering and other market-related manipulations, Sinha said the regulator is trying to curb such cases one-by-one very successfully."As far as markets are concerned, one by one we are trying to curb the manipulation very successfully -- be it IPO markets, GDR markets or secondary markets. But I must also say that this is an ongoing battle and I cannot say that we have controlled every thing," he said.Giving a "complete picture" on this menace, the Sebi chief said, "In any country or in any market, there are always people who are trying to find loopholes and take advantage."These are the people who have criminal intent. They are not here to help in the growth of the country. They work with a desire to corner money with criminal intentions."Giving example of the IPO market, Sinha said Sebi found "some people had virtually set up shops" there."If you want to raise Rs 200 crore, come to me, I will provide you the buyers, I will provide you the platform and I will provide you with a mechanism on how to go for the listing. They were manipulating the market after listing," Sinha said, while adding that Sebi was able to crack this.Sinha further said similar activities were taking place in the GDR market also, where Sebi passed some orders which have now been upheld by the Supreme Court as well."So, segment-wise, we have been able to control it -- first in IPO market and then in the GDR market. Now let us come to the secondary market."Here our insider trading regulations have been strengthened now. In addition, we found that there is a need for very active surveillance and therefore we strengthened our surveillance systems," Sinha said.These measures helped Sebi crack a major organised and syndicated financial crime that was taking place in the stock market, he added."We found that there are these companies where the price has gone up by 10-times, 20-times and even more in some cases. Our surveillance systems caught this signal and we started probing. We started asking if your share price has gone up ten times, has your business also grown. Has your profit, turnover, order book, etc grown?"We found that there was no correlation in the price and the business of these companies. Then we went to the next step and started getting into who were the buyers and sellers of these shares and from which bank account the money was coming."Then we realised that there was a racket going on. The same set of people were at play at all the levels and their intention was not just to manipulate the market, but their intention was actually to make the black money white."But they were doing it through our stock market mechanism. We caught then and we have banned more than 900 entities and my guess is that the tax avoidance that has happened in these cases is more than Rs 5000-6,000 crore," he added.