Animal rights activists scuffled with police after an international social media campaign failed to persuade authorities in Spain to spare a dog whose owner contracted ebola.

Almost 400,000 people signed a petition to save nursing assistant Teresa Romero's dog, Excalibur.

Protests erupted outside her apartment in Alcorcon, briefly stopping a police van pulling away with the family pet. Demonstrators chanted "assassins" as batons were used to clear the road.

Madrid's regional government later said the mixed-breed dog was sedated, euthanised and incinerated.

Authorities had obtained a court order to kill the dog, saying they could not rule out the possibility Excalibur could spread the virus.

On Twitter, the hashtag #SalvemosaExcalibur was tweeted more than 400,000 times in 24 hours.

Mrs Romero's husband, Javier Limon Romero, also made an emotional appeal for the dog to be spared - but the campaign was in vain.

A 2005 study published in a Centers for Disease Control and Prevention journal suggests dogs are susceptible to the virus.

However, there is no documented case of ebola spreading to people from dogs.

A US veterinary health expert criticised the Spanish authorities.

"There's never been any evidence of transmission from dogs to humans," said Dr Peter Cowen, a professor at North Carolina State University College of Veterinary Medicine.

"It's never happened in any sense. So we don't have any scientific information that that dog was a risk."