Environmental activist Greta Thunberg on Thursday denounced the ecological havoc caused by Russia's invasion of Ukraine and the lack of international reaction to the disaster.

"Ecocide and environmental destruction is a form of warfare... as Ukrainians by this point know all too well -- and so does Russia," said Thunberg, during a visit to Kyiv as part of an international delegation investigating the environmental consequences of the conflict.

"And that's why they are deliberately targeting the environment and people's livelihoods and homes and therefore also destroying lives...".

Thunberg was speaking at a news conference along with Ukrainian presidential aide Andriy Yermak.

She and the rest of the delegation also met President Volodymyr Zelensky.

The destruction of the Kakhovka dam in the southern region of Kherson on June 6 flooded huge swathes of the Kherson region. The disaster killed dozens of people and forced thousands of others to flee.

Ukraine has accused Russia of blowing up the dam, which was under Moscow's control, while the Kremlin insists that it was Kyiv that shelled the Soviet-era structure. Each side has blamed the other for the disaster.

Zelensky has criticised what he says is the lack of an adequate international response to the disaster.

"I do not think that the world reaction to this ecocide is sufficient," said Thunberg. "I don't think any reaction could be sufficient.

"So I guess we need to make more room for people who are affected by these catastrophes to tell their stories and to share information about what's happening on the ground."

"We must do everything we can to speak out about this and to try to spread awareness and share information about what is happening."

There are also fears over the risk of a disaster at Ukraine's Zaporizhzhia power station, Europe's largest nuclear plant, which is currently under Russian control.

Rafael Grossi, the head of the International Atomic Energy Agency, has repeatedly warned of the dangers of a major accident there.