Two rare tigers at the London Zoo were paired to mate in efforts to protect their species, until their first interaction turned deadly.

Sumatran tigers Asim, a male, and Melati, a female, were being introduced Friday for the first time in the same space when Asim soon became aggressive and killed Melati, the zoo said in a statement Friday.

"Everyone at ZSL London Zoo is devastated by the loss of Melati, and we are heartbroken by this turn of events," the zoo said.

Asim arrived from Denmark 10 days prior as part of a European-wide conservation breeding program.

"Asim is a handsome, confident cat who is known for being very affectionate with the ladies in his life – we're hoping he'll be the perfect mate for our beautiful Melati," head tiger keeper Kathryn Sanders said in a statement in January.

The two tigers were held in adjoining enclosures before being in the same space so that they could "see, smell and react to each other."

"As with all big cats, introductions, however carefully planned, are always considered to be high risk," the zoo said.

London Zoo was hopeful though that their interaction would be positive and said they saw good initial signs of the match.

"There has been lots of 'chuffing' which is a happy sound they make to let each other know they have good intentions. It’s fantastic to see that they’re interested in each other already," Sanders said in January.

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Asim, 7, approached Melati, 10, when the adjoining door was opened, but both tigers were cautious to begin.

"Their introduction began as predicted, but quickly escalated into a more aggressive interaction," according to the zoo.

Staff tried using flares, alarms and other loud noises to distract them, but Asim had already pounced.

Asim was coaxed into a separate enclosure, and veterinarians confirmed Melati had died, the zoo said.

The tiger exhibit was closed for the rest of the day and the zoo said staff was caring for Asim.

An endangered species, Sumatran tigers are the smallest surviving tiger subspecies, and only 400 remain, according to the World Wildlife Fund. Deforestation and poaching has devastated the species, but organizations have increased conservation efforts.

The European Endangered Species Programme, which matched Asim with Melati, tries to prevent extinction by promoting genetic diversity within the tiger population, according to the London Zoo.

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