The government today said market regulator Securities and Exchnage Board of India (Sebi) is keeping a constant vigil on the market and is taking expeditious measures wherever warranted.Regardless of the level of indices, Sebi looks into market movements and initiates appropriate action in case of any abnormality noticed in the securities market, Finance Minister P Chidambaram said in a written reply to the Lok Sabha.The market regulator has also been conducting weekly meetings with surveillance officials of the stock exchanges, he said.The stock exchanges have been advised to initiate expeditious demonstrative action wherever warranted so as to protect investors' interest and ensure orderly functioning of the stock market, Chidambaram said.Sebi and the government have been advising investors, whether small or big, that they should take informed investment decisions based on their own understanding of the market or such advice as they may receive from investment advisors.Investors should guard against rumours and also not take decisions in panic, he said. To protect the investors against impact of volatility, the risk management mechanism in the cash market has been strengthened with effect from July 10 on the lines of the practice in the derivatives market.The applicable value-at-risk margin rates are being updated at least five times in a day and exchanges have been advised to keep enhanced real time vigilance on volatility and deviance, if any, in the market, Chidambaram said.