Ukrainian President Volodymyr Zelenskyy warned of potential Russian actions as Ukraine prepares to mark its independence on Wednesday.

During his nightly address Sunday, Zelenskyy said he had spoken with French President Emmanuel Macron about “all the threats” posed by Russia, and that similar messages had been sent to U.N. Secretary-General Antonio Guterres and Turkish President Recep Tayyip Erdogan.

“All of Ukraine’s partners have been informed about what the terrorist state can prepare for this week,” Zelenskyy said.

The Ukrainian leader mentioned one action Russia may take is holding a trial for a group of Ukrainian soldiers captured during the siege of the Ukrainian city of Mariupol.

“If this despicable show trial were to go ahead … this would be the line beyond which negotiations are no longer possible,” Zelenskyy said. “There will be no more conversations. Our state has said everything.”

Thousands of deaths

Wednesday’s 31st anniversary of Ukraine’s independence from Soviet rule coincides with six months since Russia launched its invasion of Ukraine.

The war between the neighboring countries, raging since Russia’s February 24 invasion, has killed thousands of fighters on both sides and Ukrainian civilians, while forcing millions of Ukrainians to flee their homes for safety in the western part of the country, far from the front battle lines in eastern Ukraine, or go to neighboring countries.

Artillery shells hit Ukraine’s southern city of Nikopol early Sunday, not far from the Zaporizhzhia nuclear power plant.

Russia targeted sites near Odesa, Ukraine’s key Black Sea port and grain export hub. But the bombardment of Nikopol was of particular concern, with Ukrainian regional governor Valentyn Reznichenko writing on the Telegram messaging app that 25 artillery shells hit the city, setting fire to an industrial facility and cutting power to 3,000 people.

The fighting near the Zaporizhzhia nuclear power plant and Saturday’s missile strike on the southern Ukrainian town of Voznesensk, not far from Ukraine’s second-largest atomic facility, has spurred fears among world leaders of a nuclear accident.

Ukraine has asked the United Nations and other international organizations to force Russia to leave the Zaporizhzhia plant, which it has occupied since March, even as Ukrainian technicians operate the facility.

Enerhodar, a town near the plant, has recently seen repeated shelling, with Moscow and Kyiv trading blame.

Talks have been under way for more than a week to arrange for a visit to the plant by the International Atomic Energy Agency.

In a phone call Friday, Russian President Vladimir Putin told French President Emmanuel Macron that Russia would allow international inspectors to enter the plant.

Some information for this story came from The Associated Press, Agence France-Presse and Reuters.