Former Soviet leader Mikhail Gorbachev called on Tuesday for the creation of an international court to try environmental crimes, in an interview published in French daily Le Monde.

"I would personally look favourably upon creating an international tribunal to try those responsible for environmental crimes, both business leaders and the heads of state or government," the 81-year-old Nobel Peace Prize recipient said.

Gorbachev, who was in the southern French city of Marseille on Monday to speak at the Sixth World Water Forum, has led the environmental pressure group Green Cross International since 1993.

Evoking the 1986 Chernobyl nuclear disaster and the 2011 Fukushima accident, Gorbachev said his environmental group backed gradual denuclearisation in both civil and military spheres.

"For me, there is a before- and after-Chernobyl," he said of the April 1986 reactor explosion at a nuclear plant in Ukraine whose fallout spread through the western Soviet Union and a large part of Europe.

Gorbachev said he was surprised to see the trouble Japan faced in weathering the Fukushima accident.

"The Japanese are still struggling with difficulties today," he said.