At least 39 people have died and dozens more have been injured after two high-speed trains collided in southern Spain, the country's Civil Guard has said.

The incident near the city of Córdoba has been described by local officials as Spain's worst rail crash in more than a decade.

Prime Minister Pedro Sánchez is expected to visit the scene later on Monday, where rescue efforts are ongoing.

Here's what we know about the incident so far.

The crash occurred at around 19:45 local time (18:45 GMT) on Sunday, about an hour after one of the trains departed Málaga for Madrid.

The train derailed and crossed over to the opposite track, operator Adif said. It then collided with an oncoming train travelling from south Madrid to Huelva, which was forced into an embankment running alongside the track, Spain's Transport Minister Óscar Puente said on Sunday.

The majority of those killed and injured were in the front carriages of the Huelva-bound train, he added.

What caused the train to derail remains unclear. Officials say an investigation has been launched but it is not expected to determine what happened for at least a month. Puente has described the crash as 'extremely strange' and said all the railway experts consulted by the government 'are extremely baffled by the accident'.

There were around 400 passengers and staff on the two trains, operated by Iryo and Alvia, according to a statement from Renfe. It is not clear if there are people still trapped inside the carriages but rescue teams are on site.

Passengers on board the Madrid-bound train described the moment of impact feeling like an 'earthquake' and said it shattered the train's windows, displaced luggage and threw people to the floor. Emergency services continue their difficult work in a bid to reach any survivors.