A large number of technology companies including Oracle, Microsoft, and Dell run large software development and call center operations in India. But ever since the threat of terrorism increased since last year, these companies have tightened on security at their facilities.

"For a long time now, we have tightened on security at all our facilities," the Dell spokeswoman said.

Indian outsourcing companies and Indian operations of multinational technology companies were not affected by the attacks, though the disruption of train service in Mumbai on Thursday could affect the movement of staff.

The Bombay Stock Exchange in south Mumbai has shut down on Thursday. The state government has ordered schools and colleges closed Thursday.