The Oscar-nominated Japanese anime director Isao Takahata, who co-founded Studio Ghibli and was best known for his masterpiece Grave of the Fireflies, has died aged 82.

“[His death] is true, but we can’t comment further as we are trying to confirm some facts around it,” a Studio Ghibli spokeswoman said.

Citing unnamed sources related to Takahata, the public broadcaster NHK said he had died at a Tokyo hospital after a recent bout of ill health.

Takahata’s latest film, The Tale of the Princess Kaguya, earned him an Academy award nomination in 2014 for best animated feature.

It was also selected for a slot in the Directors’ Fortnight sidebar to the main competition at the 2014 Cannes film festival.

However, most consider the 1988 film Grave of the Fireflies, a moving tale of two orphans during the second world war, to be his best work.

Born in Mie prefecture in central Japan, Takahata started his career in animation at the Toei studio in 1959, where he met long-term collaborator and rival Hayao Miyazaki.

With Miyazaki, he co-founded in 1985 the Japanese animation house Studio Ghibli, which went on to produce several blockbusters.

The pair were often described by media as friends and rivals at the same time.

Over a long and distinguished career, Takahata produced around 20 films, including Only Yesterday (1991) and Pom Poko (1994).

He also produced the Miyazaki-directed 1984 film Kaze no Tani no Naushika (The Valley of the Wind), a science fantasy adventure that describes the relationship between nature and human beings.

He was also well-known for animation series Alps no Shojo Heidi (Heidi, Girl of the Alps) and Lupin Sansei (Lupin the Third).

Takahata also dabbled in politics, co-signing in 2013, with around 250 other film celebrities, a petition against a controversial state-secrets law.