Russian troops advance on the ports of Kharkiv, Ukraine's second largest city.

On Sunday, street fighting erupted in Ukraine's second-largest city, and Russian troops encircled major ports in the country's south, marking the start of a new phase of Russia's invasion after a wave of attacks on airfields and fuel facilities elsewhere in the country.

According to the Kremlin, Russia sent a delegation to Belarus for peace talks with Ukraine after making achievements on the ground. Ukraine's president recommended alternate places, claiming that Belarus had served as a staging ground for the invasion and that his country was unwilling to meet there.

Until Sunday, Russia's troops had waited on the outskirts of Kharkiv, a 1.4 million-strong city about 20 kilometres south of the Russian border, while additional forces pushed through to press the offensive farther into Ukraine and Ukrainian fighters fought back resolutely.

"We are fighting for our country, for our independence because we have the right to do so," stated Ukrainian President Volodymyr Zelenskyy.

“The past night was tough — more shelling, more bombing of residential areas and civilian infrastructure. There is not a single facility in the country that the occupiers wouldn’t consider as admissible targets.”

Videos posted on Ukrainian media and social networks showed Russian vehicles moving across Kharkiv and Russian troops roaming the city in small groups.

One video showed Ukrainian soldiers inspecting Russian light utility vehicles damaged by shelling and abandoned by Russian troops on a street.

Huge explosions lit up the sky early on Sunday near the capital, Kyiv, where terrified residents hunkered down in homes, underground garages and subway stations in anticipation of a full-scale Russian assault.

But Ukrainians also volunteered en masse to help defend Kyiv and other cities, taking guns distributed by authorities and preparing firebombs to fight Russian forces.

Russia blamed for 'state terrorism'

Zelenskyy denounced Russia’s offensive as “state terrorism.” He said the attacks on Ukrainian cities should be investigated by an international war crimes tribunal and cost Russia its place as one of the five permanent members of the United Nations Security Council.

“Russia has taken the path of evil, and the world should come to depriving it of its UN Security Council seat,” he said.

Officials maintained a 39-hour curfew to keep people off the capital’s streets until Monday morning, complicating the task of assessing the intensity of the fighting.

Zelenskyy’s office said explosions were reported at Kyiv International Airport.

Flames billowed from an oil depot near an airbase in Vasylkiv, a city 37km south of Kyiv where there has been intense fighting, according to the mayor.

Russian forces blew up a gas pipeline to the east in Kharkiv, prompting the government to warn people to cover their windows with damp cloth or gauze as protection from smoke, the president’s office said.

Meanwhile, Moscow also claimed today that its troops had “entirely” besieged the southern Ukrainian city of Kherson and the city of Berdyansk in the southeast.

“Over the past 24 hours, the cities of Kherson and Berdyansk have been completely blocked by the Russian armed forces,” defence ministry spokesman Igor Konashenkov said in a statement carried by Russian news agencies.

According to Russian state media, quoting defence officials, Moscow's soldiers have taken control of Kherson, paving the way for an assault on Odessa, a significant prize on Ukraine's Black Sea coast. However, a representative for the Ukrainian Defense Ministry stated that "the struggle goes on." The mayor of Kherson claimed Russian forces had been to his office to discuss how the city's 300,000 people might get about. Nonetheless, the mayor stated on Facebook that "the flag over us is Ukrainian."

On the seventh day of battle, images of bombs ripping through civilian infrastructure provoked a new round of harsh criticism of Moscow, with the United Nations General Assembly voting 141 to 5 to condemn Russia's conduct, with 35 abstentions.