Pfizer has postponed the delivery of new batches of its coronavirus vaccine to eight European nations including Spain, the Spanish health ministry said Monday, a day after the EU began its immunisation campaign.

The Spanish branch of Pfizer informed Madrid on Sunday night of the delay in shipments to the eight nations due to a "problem in the loading and shipment process" at its plant in Belgium, the health ministry said in a statement.

It did not specify which European nations aside from Spain were affected.

Pfizer has informed the ministry that the problem "was already resolved" but the next delivery of vaccines "will be a few hours late" and arrive in Spain on Tuesday, a day later than expected, the statement said.

Asked about the delay during an interview with radio Ser, Health Minister Salvador Illa said it was due to a problem "linked to the control of the temperature" of the shipments which was "apparently fixed".

The vaccine must be stored at ultra-low temperatures of about -70 degrees Celsius (-112 Fahrenheit) before being shipped to distribution centres in specially designed cool boxes filled with dry ice.

Once out of ultra-low temperature storage, the vaccine must be kept at 2 Celsius to 8 Celsius to remain effective for up to five days.

Spain is scheduled to received 350,000 doses of the Pfizer-BioNTech coronavirus vaccine per week over the next three months.

Most European Union nations began their immunisation campaigns against the virus this weekend with the Pfizer-BioNTech jab, beginning with the elderly, health care workers and politicians.