Ukraine's state nuclear agency Enerhoatom has warned against an increasing risk of fire and radiation due to the shelling of the Russian-occupied Zaporizhzhya nuclear power plant.

"The Zaporizhzhya nuclear power plant is operating at risk of violating the norms of radiation and fire protection," the agency said on Telegram, following an attack on the site on Saturday.

Shelling the previous day damaged a nitrogen plant and an auxiliary part of the power plant, dpa news agency quoted Enerhoatom as saying.

"There remains a risk of hydrogen leaking and radioactive particles dispersing, and the risk of fire is also high."

Ukrainian power plant personnel are trying to maintain safety levels despite these conditions but the threat due to the occupation of the power plant by Russian troops, however, remains high.

The plant may have been mined by Russian troops, according to a report by The Insider which is critical of the Kremlin.

A video allegedly shot at the beginning of the week showed Russian military trucks driving onto the factory site and unloading goods.

One of the trucks drove into the plant's engine room.

The Insider said either the power plant itself or the area around it has been mined.

"The EU condemns Russia's military activities around the Zaporizhzhya nuclear power plant, which is a serious and irresponsible breach of nuclear safety rules and another example of Russia's failure to respect international norms," said EU foreign affairs chief Josep Borrell, demanding access for the International Atomic Energy Agency (IAEA) to the plant.

On March 4, the nuclear and thermal power stations were both captured by Russian forces.

The plant continues to be operated by Ukrainian staff, under Russian control.

Last week, IAEA chief Rafael Grossi expressed grave concerns about the physical integrity of the plant, whether all necessary repairs and maintenance were being done, and the security of nuclear material.