A private Cessna plane has crashed into the Baltic Sea off Latvia's coast in mysterious circumstances.

Nato jets were scrambled to follow the plane on its erratic flight which began in southern Spain.

Officials say the plane - believed to have had four people on board - had been due to land in Cologne, Germany, but instead headed out into the Baltic.

Nato pilots and Swedish officials tracking the plane could see no-one in the cockpit.

“The aircraft was flying from Spain to Cologne, but during the flight the aircraft changed its flight route,” the Latvian Civil Aviation Authority said in a statement.

“Air traffic controllers were unable to communicate with the aircraft's crew,” it said, adding that the Cessna 551 was registered in Austria - but the owner was in Spain.

Meanwhile, the FlightRadar24 data tracking website said the aircraft took off from the Spanish city of Jerez de la Frontera at 12:56 GMT.

At 17:37 it was listed on FlightRadar24 as losing speed and altitude.

German newspaper Bild said the plane had reported cabin pressure problems after take-off and contact was lost after it had cleared the Iberian Peninsula.

Fighter jets from several countries followed the Cessna on its journey.

Rescue teams from Latvia, Sweden and Lithuania arrived at the crash area soon after after reports that the plane had fallen into the sea near the Latvian city of Ventspils.

The aircraft crashed “when it ran out of fuel,” Sweden's search and rescue operation leader Lars Antonsson later told AFP, adding that “no human remains have been found”.

Mr. Antonsson said that rescuers “have no explanation at all, we can only speculate” about what happened “but they [the people on board] were clearly incapacitated on board”. (BBC)

•PHOTO:The Cessna Citation 551 jet, which had taken off from the Spanish city of Jerez in the afternoon, disappeared from radar while flying over the Baltic Sea northwest of the Latvian port city of Ventspils, Swedish news agency TT reported. Urbanandsport/NurPhoto via Getty Images