Even though security experts said they doubted the authenticity of the e-mail messages, given the deadly terrorist attacks Mumbai last week, airport authorities weren't taking chances, the Voice of America reported.

Security efforts, including closer and repeated luggage inspection, have been increased at airports in New Delhi, Bangalore and Chennai, officials said.

The threatening e-mails sent to media organizations have been traced to a computer relay server in Saudi Arabia, VOA reported. Analysts said they couldn't match the pattern and language of previous credible communications from the group known as Deccan Mujahideen.