NEW DELHI, Nov 9: Security at airports in South India has been heightened after the Trichy Airport Director received a letter threatening terror attacks, news agencies said on Thursday.

The letter said: "Al Qaeda terrorists are going to bomb Chennai airport. It added that suicide squads have penetrated airports in Chennai, Trichy, Madurai, Coimbatore and airports in Kerala."

However, the Tamil Nadu police says, there are no specific intelligence inputs to corroborate the contents of the letter but they are taking no chances and will increasingly monitor vehicle entry inside the Chennai Airport.

Authorities at other airports are also taking the threat seriously. They have put in place additional security measures, ness reports said. There is an increased checking of passengers and their baggage is being randomly checked.

Even the Bangalore airport, which is not mentioned in the letter has been put on high alert. An anti-hijacking squad has been alerted in Karnataka and Mangalore, Bangalore and Hubli airports have been put on high alert.