MADRID -- At least 21 people were confirmed dead, and 25 others were seriously injured after two high-speed trains derailed and collided near the city of Cordoba in southern Spain on Sunday, according to authorities.

In addition, around a hundred passengers reportedly suffered minor injuries. The accident occurred at around 19:45 local time (1845 GMT) when a train carrying 317 passengers on the Malaga-Madrid route went off the rails for reasons still unknown near Amaduz, about 20 km from Cordoba, Spanish authorities said.

The derailed train struck another high-speed train travelling on an adjacent track from Madrid to Huelva, causing the second train to also leave the rails.

Spain's Transport Minister Oscar Puente described the collision as a "terrible impact," saying the last two wagons of the Malaga-Madrid train derailed and struck the first two wagons of the oncoming train, sending them off the tracks.

Emergency services from the region of Andalusia were deployed on the scene, while local residents had come to help transfer people with minor injuries to a nearby sports centre for first aid.

Spain's Military Emergency Unit was also mobilised to assist in rescue work. Rail services on the affected line have been suspended until at least Tuesday, authorities said.

Spanish Prime Minister Pedro Sanchez said on social media that he and his government are closely following the accident. Spain's Royal Family has also extended condolences to the families of the victims.

Rescue operations are still ongoing late on Sunday as officials warned that the number of dead and injured could change in the coming hours.

Rail infrastructure operator Adif said it had opened an area at Atocha Station in Madrid, as well as in Malaga and Huelva, to provide information for relatives of affected passengers. A dedicated phone line has also been set up.

The previous deadliest train accident in Spain occurred in July 2013, when 79 people were killed after a high-speed train derailed while entering the city of Santiago de Compostela due to excessive speed.