KYIV, Ukraine (AP) — Russian airstrikes targeted Ukraine’s energy facilities again Thursday as the first snow of the season fell in Kyiv, a harbinger of the hardship to come if Moscow’s missiles continue to take out power and gas plants as winter descends.

Separately, the United Nations announced the extension of a deal to ensure exports of grain and fertilizers from Ukraine that were disrupted by the war. The deal was set to expire soon, renewing fears of a global food crisis if exports were blocked from one of the world’s largest grain producers.

Even as all sides agreed to extend the grain deal, air raid sirens sounded across Ukraine on Thursday. At least seven people were killed and more than two dozen others wounded in the drone and missile strikes, including one that hit a residential building, authorities said.

The Kremlin’s forces have suffered a series of setbacks on the ground, the latest being the loss of the southern city of Kherson. In the face of those defeats, Russia has increasingly resorted to aerial onslaughts aimed at energy infrastructure and other civilian targets in parts of Ukraine it doesn’t hold.

Russia on Tuesday unleashed a nationwide barrage of more than 100 missiles and drones that knocked out power to 10 million people in Ukraine — strikes described by Ukraine’s energy minister as the biggest assault yet on the country’s battered power grid in nearly nine months of war.

It also resulted in a missile landing in Poland, killing two people. Authorities still were trying to ascertain where that missile came from, with early indications pointing to a Ukrainian air defense system seeking to counter the Russian bombardment.

Polish President Andrzej Duda on Thursday visited the site where the missile landed and expressed understanding for Ukraine’s plight. “It is a hugely difficult situation for them and there are great emotions, there is also great stress,” Duda said.

The renewed bombings come as many Ukrainians are coping with the discomforts of regular blackouts and heating outages. A light snow dusted the capital Thursday, where the temperature fell below freezing. Kyiv’s military administration said air defenses shot down four cruise missiles and five Iranian-made exploding drones.

In eastern Ukraine, Russia “launched a massive attack on gas production infrastructure,” said the chief of the state energy company Naftogaz, Oleksiy Chernishov. He did not elaborate.

Russian strikes also hit the central city of Dnipro and Ukraine’s southern Odesa region for the first time in weeks and hit critical infrastructure in the northeastern Kharkiv region near Izium, wounding three workers.

The head of Ukraine’s presidential office, Andriy Yermak, called the strikes on energy targets “naive tactics of cowardly losers.”

“Ukraine has already withstood extremely difficult strikes by the enemy, which did not lead to results the Russian cowards hoped for,” Yermak wrote Thursday on Telegram.

Ukrainian President Volodymyr Zelenskyy said in his nightly video address that 10 million people in Ukraine were without power on Thursday as well, mainly in the Kyiv, Odesa, Sumy and Vinnytsia regions. Ukraine had a prewar population of about 40 million.

Zelenskyy earlier posted on Telegram a video that he said was of one of the blasts in Dnipro. The footage from a vehicle dashboard camera showed a fiery blast engulfing a rainy road.

“This is another confirmation from Dnipro of how terrorists want peace,” Zelenskyy wrote, referring to the Kremlin’s forces. “The peaceful city and people’s wish to live their accustomed lives. Going to work, to their affairs. A rocket attack!”

Valentyn Reznichenko, governor of the Dnipropetrovsk region, said a large fire erupted in Dnipro after the strikes there hit an industrial target. The attack wounded at least 23 people, Reznichenko said.

Russia’s Defense Ministry said the strikes in Dnipropetrovsk hit a factory that produces military rocket engines.

In the Odesa region, an infrastructure target was hit, Gov. Maksym Marchenko said on Telegram, warning about the threat of a “massive missile barrage on the entire territory of Ukraine.”

Elsewhere, a Russian strike that hit a residential building killed at least seven people overnight in Vilniansk in the southern region of Zaporizhzhia. Rescuers combed the rubble Thursday, searching for any other victims.

Officials in northeast Ukraine’s Poltava and Kharkiv regions and the Khmelnytskyi and Rivne regions in the west urged residents to stay in bomb shelters.

The U.N. nuclear watchdog has warned that the repeated strikes on Ukraine’s electricity grid were endangering the country’s nuclear power plants. The reactors need power for cooling and other essential safety functions, and their emergency generators can only provide back-up electricity for a limited period of time.

A nuclear plant in Khmelnytskyi was cut off from the electricity grid on Tuesday, forcing it to temporarily rely on diesel generators and to shut down its two reactors, the International Atomic Energy Agency said. Another plant in Rivne disconnected one of its four reactors after partially losing connection to Ukraine’s outside grid.

IAEA Director-General Rafael Grossi said the power loss at the Khmelnytskyi plant “clearly demonstrates that the nuclear safety and security situation in Ukraine can suddenly take a turn for the worse, increasing the risk of a nuclear emergency.”

Grossi also has expressed grave concerns about the potential for a radiation leak at the Zaporizhzhia Nuclear Power Plant, Europe’s largest, which has been held by Russian forces for most of the war.

The war’s impact has been felt far beyond Ukraine, in global food and energy markets. Ukraine and Russia are among the world’s largest exporters of grain, and Russia is also a significant producer of fertilizer.

There were concerns in recent days about the fate of the deal brokered by the U.N. and Turkey that created a safe shipping corridor in the Black Sea to address wartime disruptions of grain exports. The deal was set to expire Saturday, but U.N. Secretary-General António Guterres said it had been extended for 120 days.

In addition to securing the safe passage of Ukrainian exports, Guterres said the United Nations is also “fully committed” to removing obstacles that have impeded the export of food and fertilizer from Russia.

The Russian Foreign Ministry confirmed the extension, and Zelenskyy called it a “key decision in the global fight against the food crisis.”