NEW DELHI — Satyam Computer Services, a leading Indian outsourcing company that serves more than a third of the Fortune 500 companies, significantly inflated its earnings and assets for years, the chairman and co-founder said Wednesday, roiling Indian stock markets and throwing the industry into turmoil.

The chairman, Ramalinga Raju, resigned after revealing he had systematically falsified accounts as the company expanded from a handful of employees into a back office giant with a work force of 53,000 and operations in 66 countries. Raju said Wednesday that 50.4 billion rupees, or $1.04 billion, of the 53.6 billion rupees in cash and bank loans the company listed in assets for its second quarter, which ended in September, were nonexistent.

Revenue for the quarter was 20 percent lower than the 27 billion rupees reported, and the company’s operating margin was a fraction of what it declared, he said Wednesday in a letter to directors that was distributed by the Bombay Stock Exchange.

Satyam serves as the back office for some of the largest banks, manufacturers, health care and media companies in the world, handling everything from computer systems to customer service. Clients have included General Electric, General Motors, Nestle and the U.S. government. In some cases, Satyam is even responsible for clients’ finances and accounting.

The revelations could cause a major shake-up in India’s enormous outsourcing industry, analysts said, and may force many large companies to investigate and perhaps revamp their back offices. News of the scandal — quickly compared with the collapse of Enron — sent jitters through the Indian stock market, and the benchmark Sensex index fell more than 5 percent. Shares in Satyam fell more than 70 percent.

The size and scope of the fraud raises questions about regulatory oversight in India and beyond. Satyam has been listed on the New York Stock Exchange since 2001, and on Euronext since January 2008. The company has been audited by PricewaterhouseCoopers since its listing on the New York Stock exchange.