Apparently over security concerns, the authorities on Friday advance the arrival of Prime Minister Narendra Modi to the airport here by an hour on Saturday in order to enable him to take a helicopter ride to the city proper.

Modi was earlier scheduled to arrive at 5 p.m. and go straight to the Old Currency Building in central Kolkata for an official programme.

But as per the changed schedule, Modi will now arrive by an Indian Air Force flight at 4 p.m., and then he would be flown in a helicopter to the city's Race Course.

With the early onset of evening in the ongoing winter season, it wouldn't have been possible for the helicopter to land in Race Course had the prime minister arrived at 5 p.m.

Stringent security is being put in place for the Prime Minister's tour, amid security forces' apprehensions that a couple of organisations could try to organise large-scale protests including black flag demonstrations at the NSCBI Airport and on the streets.

There has been a social media campaign with the hashtag #GoBAckModi asking people to rally at the airport and also on VIP Road to prevent the Prime Minister from entering the city.

Also, it has now been decided that the Prime Minister would go to Belur Math - global headquarters of the Ramakrishna Math and Ramakrishna Mission - on a launch over the river Ganga.

However, there could be last minute changes in the Prime Minister's schedule in view of intensifying protests in the city and the rest of Bengal on the issue of the Citizenship (Amendment) Act and the violence in Jawaharlal Nehru university (JNU).