On Thursday, Russian forces fought for control of a vital energy-producing city in Ukraine’s south and gained ground in their bid to cut the country off from the sea, as Ukrainian leaders urged citizens to wage guerrilla warfare against the invaders.

Fighting for the southern city of Enerhodar, a Dnieper River hub that accounts for roughly one-quarter of the country’s power generation, erupted as the two sides met for another round of talks aimed at halting the fighting that has displaced over 1 million people.

The mayor of Enerhodar, home to Europe’s largest nuclear power plant, said Ukrainian forces were fighting Russian troops on the city’s outskirts. Dmytro Orlov urged residents not to abandon their homes. Moscow’s advance on Ukraine’s capital appears to have stalled in recent days, with a massive armored column north of Kyiv at a standstill, but the military has made significant gains in the south as part of an effort to cut Ukraine off from the Black and Azov seas.

The Russian military announced that it had taken control of Kherson, and local Ukrainian officials confirmed that forces had taken over the local government headquarters in the vital Black Sea port of 280,000 people, making it the first major city to fall since the invasion began a week ago.

Heavy fighting raged on the outskirts of another strategic port on the Azov Sea, Mariupol, plunging it into darkness, isolation, and fear. Electricity and phone service were mostly out, and food and water were scarce in homes and businesses.

Without phone service, medics had no idea where to take the injured.

Cutting Ukraine’s access to its Black Sea and Azov coasts would cripple the country’s economy and allow Russia to build a land corridor stretching from its border, across occupied Crimea, and all the way west to Romania.

According to the office of Ukrainian President Volodymyr Zelenskyy, a second round of talks between Ukrainian and Russian delegations has begun in neighboring Belarus.

However, the two sides appeared to have little in common prior to the meeting, and Russian President Vladimir Putin warned Ukraine that it must quickly accept the Kremlin’s demand for “demilitarization” and declare itself neutral, effectively abandoning its bid to join NATO.

Putin has long claimed that Ukraine’s shift toward the West poses a threat to Moscow, which he used to justify the invasion.

According to an official in the French president’s office, Putin told French President Emmanuel Macron that he was determined to continue his attack “until the end.”

Despite a plethora of evidence of civilian casualties and civilian infrastructure destruction by the Russian military, Putin dismissed accusations that his forces had attacked residential areas as part of a “anti-Russian disinformation campaign” and insisted that Russia uses “only precision weapons to exclusively destroy military infrastructure.”

Ukrainian negotiator David Arakhamiya stated that Kyiv’s main demand in the talks would be the creation of humanitarian corridors to allow civilians to flee to safety. Ukraine, too, was seeking a cease-fire.

Ukrainians who remained in the country faced another bleak day. Long lines formed outside the few pharmacies and bakeries that remained open in Kyiv, as snow gave way to a cold, gray drizzle.

New shelling was reported in the northern city of Chernihiv, where at least 22 civilians were killed in a Russian bombardment of a residential area, according to emergency officials. They warned that as rescuers search the debris, the number of casualties could rise. The mayor stated that he was working hard to organize safe passage for civilians.

Families with children fled via muddy and snowy roads in Donetsk’s eastern region, while military strikes on the village of Yakovlivka near Kharkiv’s eastern outskirts destroyed 30 homes, killing three and injuring seven, and rescuers rescued ten people from the ruins, according to emergency officials.

Ukrainian authorities called on the people to wage guerrilla warfare against Putin’s forces by cutting down trees, erecting barricades in the cities and attacking enemy columns from the rear.