Dublin Zoo says it is 'deeply saddened' by the unexpected death of its female western lowland gorilla, Lena.

The 35-year-old had given birth to seven offspring since her arrival at the zoo in 1988, when she was just four.

The zoo says she passed away on Friday August 10th, after being unwell for some time.

She had been receiving round-the-clock intensive care from animal care and veterinary teams over several weeks.

But the zoo says the exact reason for her death is not known.

Management say they are awaiting the results of a post mortem.

"The team at Dublin Zoo is extremely saddened by this loss", they add.

Dublin Zoo has maintained western lowland gorillas for many years and has been home to a breeding group of seven healthy gorillas, including Lena.