NEW DELHI - India's federal railways Thursday ordered cancellation of all tickets for regular passenger trains until June 30 booked ahead of imposition of COVID-19 lockdown in the country, officials said.

However, the Shramik Special trains ferrying migrant workers back to their native place, and passenger trains that started running this week between Delhi and 15 major stations will continue to operate as scheduled.

"Regular passenger service including mail, express, passenger and suburban services cancelled until further order. Booked tickets for these trains for period up to June 30 will be cancelled," a railway official said.

According to railways, a full refund will be given to all passengers whose tickets stand cancelled.

All passenger trains were suspended since March 22, three days before the start of a nationwide lockdown in the country. The lockdown restrictions were imposed to break the COVID-19 chain of transmission.

Earlier this month government started special trains for the stranded migrant workers. On Sunday the railways announced plans to restart passenger trains in a phased manner.

"As on 13th May 2020, a total of 642 'Shramik Special' trains have been operationalized from various states across the country. Around 790,000 passengers have reached their home state," a statement issued by railways said.

As May 17 will mark the end of the third phase of the coronavirus lockdown, the government is all set to impose a fourth phase with a new set of rules.

Indian sprawling railways is the world's third largest network, that used to ferry around 23 million people a day.

Ahead of lockdown, around 12,000 trains were being run each day, reports said.