International airports in the Indian cities of Mumbai, Chennai and Hyderabad were placed on the highest security alert on Sunday after police received information of a possible aircraft hijacking attempt, officials and news reports said.
"We have increased and strengthened patrolling and access control at all three airports," said OP Singh, director general of the Central Industrial Security Force (CISF), which looks after airport security. 
The alert was sounded after Mumbai police received information of possible hijack attempt, NDTV news channel reported.
All airlines have been asked to remain extra vigilant and avoid last-minute check-ins, Singh said. 
"Passengers have been requested to cooperate and additional numbers of sniffer dogs have been deployed at all three airports," Singh added.