MUMBAI: As a probe continues into the misuse of stock markets for evading taxes and laundering black money, 4-5 cartels of market operators have been identified for making illicit gains or showing fictional losses of several thousands of crores of rupees over last 2-3 years.According to sources, both 'bull' and 'bear' cartels appear to be at work in the entire scheme of things, while they are estimated to have assisted over 1,000 entities -- including individuals, listed companies and their promoters and top executives -- in tax evasion and money laundering A bear cartel acts in concert to push down the share prices to show losses that are eventually used to neutralise tax demand of the customer from his or her other income.On the other hand, another type of cartel creates a bullish trend or a sharp rise in share prices to make undue gains in stocks of little-known companies to launder black money through stocks and show the same as legitimate gains.A large number of small NBFCs and brokers are already under Sebi 's scanner for having facilitated illicit transactions worth thousands of crores of rupees over the past 2-3 years, sources said.It has emerged during investigations by Sebi and stock exchanges that such illicit activities tend to accelerate during last few months of a fiscal and quantum of such transactions has grown manifold in the last few years.Besides, a number of such entities, which includes both individuals and corporate brokerage firms, have been found to be repeat offenders for various offences in the securities market and many of them create new shell companies to hide their past precedents.Those under the scanner also include some listed firms and their promoters, who regularly offer their services for channelising black money and for evading taxes through use of stock exchange platforms.While it may be difficult to quantify the entire value of black money laundered through stock markets, as also the total tax amounts evaded through this platform, sources said that the total figure may easily run into several thousands of crores of rupees given the spread of such illicit activities.In just two cases, where Sebi last week passed interim orders, total illicit gains estimated worth Rs 500 crore have come to the fore in case of a select few entities.Besides, being possible cases of money laundering or tax evasion, Sebi has found such activities to be securities market frauds as well, as they involve manipulative transactions in securities and misuse of the market.In its biggest ever crackdown for suspected tax evasion and laundering of black money through stock trading platforms, Sebi on Friday barred 260 entities, including individuals and companies, from the securities markets.While Sebi would further probe these cases, it has referred the matter to the Income Tax Department, Enforcement Directorate, Financial Intelligence Unit, among other agencies, for necessary actions on their part.