New Delhi: Regulator Sebi and stock exchanges have beefed up their surveillance mechanism to check any manipulative activities in the market this week in view of the high-octane election related events lined up. The heightened surveillance and monitoring systems are already in place for Monday, the first trading session after the announcement of exit poll results, while they would be further ramped up on Thursday, when the final results will be declared, a senior official said. The poll results are likely to have a bearing on trading and increased monitoring helps to keep in check possible manipulations and excessive volatility in the markets. Manipulators tend to exploit such volatile situations in the stock markets. The enhanced vigil on the markets will continue till May 23, when the results of the Lok Sabha polls will be declared. According to the official, movements in Nifty futures and options on the Singapore exchange will also be closely monitored. Trading in Singapore stock exchange starts much before Indian markets open and their trends generally have an impact on domestic markets. The BSE Sensex soared 537 points and the NSE Nifty reclaimed the 11,400 level Friday in a broad-based rally ahead of the poll results.