Authorities in Singapore on Friday warned of travel delays as a result of technical troubles at its entry points, as long queues formed at immigration checkpoints at its main international airport and border crossings with Malaysia.

The city-state's immigration agency said it was "experiencing system slowness at selected passenger clearance checkpoints", including at Changi Airport, one of the busiest gateways in the world, and two land border crossings with Malaysia.

The airport warned passengers to expect delays while immigration authorities urged travellers to postpone non-essential travel.

Changi handles nearly 150,000 passengers a day while about 300,000 people cross daily at the Woodlands and Tuas causeways linking Singapore with Malaysia.

Posts on social media since late morning showed long queues at the airport with lines at immigration counters snaking out of the departure hall and past check-in counters.

Two Reuters journalists at the airport said by mid-afternoon the problems had eased.

With technical issues affecting automated immigration lanes, travellers had been redirected to immigration officers instead and extra personnel had been deployed to help clear passengers. (Reporting by Xinghui Kok; Editing by Kanupriya Kapoor, Martin Petty)