KYIV, Ukraine (AP) — Russia’s troops fought Thursday to regain lost ground in areas of Ukraine that Russian President Vladimir Putin has illegally annexed while Moscow tried to pound the invaded country into submission with more missile and drone attacks on critical infrastructure.

Russian forces attacked Ukrainian positions near Bilohorivka, a village in the Luhansk region of eastern Ukraine. In the neighboring Donetsk region, fighting raged near the city of Bakhmut. Kremlin-backed separatists have controlled parts of both regions for 8½ years.

Putin declared martial law in Luhansk, Donetsk and southern Ukraine’s Zaporizhzhia and Kherson regions on Wednesday in an attempt to assert Russian authority in the annexed areas following a string of battlefield setbacks and a troubled troop mobilization.

The unsettled status of the illegally absorbed territory was especially visible in the Kherson region’s capital, where military officials have replaced Kremlin-installed civilian leaders amid a mass evacuation and an ongoing Ukrainian counteroffensive.

Kherson city was one of the first urban areas captured by Russia when it invaded Ukraine, and it remains a prime target for both sides because of its key industries and major river port. Thousands of the city’s 250,000 residents streamed out of the city in anticipation of intensified assaults.

President Volodymyr Zelenskyy’s office said Thursday that Ukrainian forces continued to engage the enemy, mounting 15 attacks on Russian military strongholds in the Kherson region.

Meanwhile, Russia continued its stepped-up attacks on Ukraine’s energy infrastructure, dispatching drones and missiles to eight regions. At least three civilians died and 14 were wounded in overnight attacks across Ukraine, according to the Ukrainian president’s office.

In Kryvyi Rih, Russian strikes damaged a power plant and another energy facility, cutting electricity to the central Ukraine city of about 600,000 residents. Apart from being Zelenskyy’s hometown, Kryvyi Rih is home to several large metallurgical factories that are key to Ukraine’s economy. Regional governor Valentin Reznichenko said the city sustained serious damage.

Ukrainian authorities said missile and drone strikes ignited several fires in the southern city of Mykolaiv, with four drones hitting a school. Another school in Komyshuvakha, a village in the Zaporizhzhia region, also took four drone strikes and sustained damage. Authorities reported no casualties.

Russia’s sustained attacks on Ukraine’s infrastructure prompted authorities to ask residents to reduce their energy consumption from 7:00 a.m. to 11:00 a.m. starting Thursday and to dim city street lights. They warned of rolling blackouts.

“Now, every illuminated business sign, billboard or washing machine can lead to serious emergency shutdowns,” Reznichenko said.

Despite the Kremlin’s claims to the contrary, a leading Russian military expert unwittingly acknowledged that Iran has supplied Russia with drones it uses in Ukraine.

Ruslan Pukhov, head of the Moscow-based think tank Center for Analysis of Strategies and Technologies, asked journalists before a television interview not to ask him where the drones came from, unaware that he was live on air.

Pukhov said that “we all know that they are Iranian-made, but authorities haven’t acknowledged that.”

Russian Foreign Ministry spokeswoman Maria Zakharova on Thursday dismissed reports that Moscow is using Iranian-made drones in Ukraine as “rumors” and “far-fetched assumptions.”

In Brussels, the European Union on Thursday imposed sanctions on Iran’s Shahed Aviation Industries as well as three Iranian armed forces generals for undermining Ukraine’s territorial integrity by helping to supply Russia with drones.

In another sign of Russia’s wavering mobilization, Ukrainian authorities said more than 3,000 Russians have so far called a dedicated hotline for those who don’t want to take part in the war and want to surrender.

Hotline spokesman Vitalii Matvienko said more recently-drafted Russian soldiers are calling now, with some reaching out in tears out of fear of the possibility that they’ll be drafted.

“When the Ukrainian counteroffensive is advancing, the number of calls is rising,” Matvienko told The Associated Press in an interview.

Ukraine says it guarantees the safety of anyone who surrenders in line with international law and that they can either return to Russia or apply to live in some European Union countries or in Ukraine.

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Hanna Arhirova in Kyiv, and Lorne Cook in Brussels, contributed to this report.

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