Indonesia set up roadblocks on Monday to screen for Covid-19 among travellers returning from Muslim holidays, as fears rose that mass gatherings and virus variants could trigger a surge of new cases in the world's fourth most populous nation.

Each year millions of Indonesians fan out across the sprawling archipelago after Ramadan to celebrate Id ul-Fitr and visit extended families, in a tradition known as “mudik”.

To try and avoid mass transmission of the virus, the authorities banned travel between May 6 and 17, during the Id period, but government data suggests that at least 1.5 million people left their homes ahead of the ban.

On Monday, the police were stopping cars at checkpoints around Jakarta in an attempt to identify and isolate positive cases.