Environmental campaigners said Sunday they were taking legal action against a French marine park, Europe's largest, over the treatment of its orca whales and other animals after many were killed in a recent storm.

The Antibes Marineland reopened a week ago after suffering severe damage in deadly storms that struck the Cote d'Azur, on France's Mediterranean coast, in October.

Many animals and fish at the park were killed in the storm, including Valentin, a 19-year-old orca whale which succumbed to internal injuries a week later.

The park was deluged with mud, killing sharks, sea lions and turtles because it was left without electricity to pump in clean water.

International NGO Sea Shepherd organised a protest attended by around 250 people outside the park on Sunday, saying the orca enclosures remain highly unsatisfactory and the animals should never have been subject to such dangers in the first place.

"We are against the keeping of orca whales in captivity because it is simply not where they should be," Paul Watson, founder of the NGO, told reporters.

There has been growing global opposition to keeping orcas, also known as killer whales, in captivity, particularly since the release of a widely seen 2013 documentary Blackfish on the treatment of orcas at SeaWorld in the United States.

An employee trains orcas in a pool water of the Marineland theme park on the French riviera city of Antibes on March 17, 2016 Valery Hache, AFP/File

SeaWorld announced earlier this month that it would no longer breed captive orcas and that the current generation would effectively be its last.

Sea Shepherd has lodged a legal complaint against Antibes Marineland, saying the park mistreats its animals and pollutes the local environment. It expects a first hearing to be held in September.

Marineland denies charges of mistreatment and said in a statement on Sunday that "the conditions of well-being of the marine mammals are carefully and strictly controlled by several organisations, as well as European and international regulations."

The park is already subject to a preliminary investigation following complaints of animal cruelty by three French NGOs.