An anonymous e-mail threatening to blow up the Kempegowda International Airport Limited (KIAL) in Bangalore prompted authorities to step up security.
"We have received a bomb threat here yesterday," KIAL said in a statement in Bangalore.
An FIR has been lodged with Bangalore Police, it said adding all airlines and partners have been put on alert.
The airport has been on high alert since January 26 and would continue to be so till the month end, KIAL said, adding that security has been strengthened in the facility by intensifying checking and patrolling.
"Heightened security alert, which was done for Republic Day, will continue till January 31 as directed by the Bureau of Civil Aviation Security," KIAL said.
Airport operations, however, remained normal, it said.