LONDON (REUTERS) - Two tigers have died in separate fights at British zoos in the past week, leaving their keepers devastated.

On Monday, a 13-year-old Siberian female called Shouri was killed at Longleat Safari Park in south-west England when she managed to enter the adjacent paddock of two other tigers through an open door.

"As a result, a fight ensued between the three," the zoo said on its website. "A full investigation is ongoing to determine the exact circumstances surrounding this terribly sad event.

"The dedicated team of keepers who care for our big cats are, understandably, extremely distraught by the events and we are doing everything we can to help and support them."

The park was closed at the time and neither of the other two tigers was injured.

The incident happened just three days after a female Sumatran tiger at London Zoo, 10-year-old Melati, was fatally attacked by a new male tiger moments after they were introduced by zookeepers last Friday.

Asim, seven, had arrived as a potential mate from a Denmark zoo and the two had appeared to getting on well in the 10 days before the incident, albeit separated by mesh.

"After careful observation, we all felt confident that the timing was right to introduce Asim to Melati," Ms Kathryn England, chief operating officer at ZSL London Zoo wrote in an online post.

Keepers had been ready for their first meeting.

"The team were not empty-handed; big cat introductions tend to be highly charged and always carry risk," Ms England wrote. "Fire extinguishers, airhorns, hoses and flares were at the ready to distract them if the encounter took a dangerous turn."

Although the first few minutes went as planned, the mood quickly changed.

"In the blink of an eye, with no obvious provocation, they turned on each other and our years of experience told us it was beyond normal," Ms England wrote.

"Everyone was numb with shock, and the sheer disbelief was palpable."