A huge convoy of Russian tanks and other military vehicles has massed near Ukraine’s capital, Kyiv, on the sixth day of Russia’s war on Ukraine.

So far, the Russian military’s movements have been stalled by fierce resistance on the ground and a surprising inability to dominate the airspace. Many Ukrainian civilians, meanwhile, spent another night huddled in shelters, basements or corridors.

On Monday, after a first, five-hour session of talks between Ukraine and Russia yielded no stop in the fighting, both sides agreed to another meeting in the coming days. As the talks along the Belarusian border wrapped up, several blasts could be heard in Kyiv and Russian troops advanced on the city of nearly 3 million.

Elsewhere, video from Kharkiv, Ukraine’s second-biggest city with a population of about 1.5 million, showed residential areas being shelled, with apartment buildings shaken by repeated, powerful explosions.

Authorities in Kharkiv said several people had been killed and dozens injured. They warned that casualties could be far higher.

The Russian military has denied targeting residential areas despite evidence of shelling of homes, schools and hospitals.

Fighting raged in other towns and cities, too. The strategic port city of Mariupol, on the Sea of Azov, is “hanging on” said Ukrainian President Volodymyr Zelenskyy’s adviser Oleksiy Arestovich. An oil depot was reported bombed in the eastern city of Sumy.

Russian artillery hit a military base in Okhtyrka, a city between Kharkiv and Kyiv, and more than 70 Ukrainian soldiers were killed, the head of the region wrote on Telegram. Dmytro Zhyvytskyy also posted photographs of the charred shell of a four-story building and rescuers searching rubble.

Separatist-controlled territories in the east continued to be shelled as Russia pressed on with the invasion. One death was reported.