Security at Yes Bank headquarters,its branches and ATMs across Mumbai was tightened to avert any untoward incident, as hundreds of account holders of the crisis-hit private lender rushed to withdraw money, an official said on Friday.The RBI on Thursday imposed a moratorium on the capital-starved Yes Bank, capping withdrawals at Rs 50,000 per account.Account holders rushed to branches of the bank and their ATMs in panic to withdraw money on Friday morning, leading to chaos at many centres, including the one in south Mumbai's Fort area."We have deployed police personnel outside the bank headquarters, its branch offices and ATM centres in the city to avert any kind of law and order issue," a spokesperson of the Mumbai Police said.The police are constantly monitoring the situation and so far, no untoward incidents have been reported, he said.