KYIV, Ukraine (AP) — Russian forces shelled Ukraine’s second-largest city on Monday, rocking a residential neighbourhood, and closed in on the capital Kyiv – in a 17-mile convoy of hundreds of tanks and other vehicles as talks aimed at stopping the fighting yielded only an agreement to keep talking.

Amid ever-growing international condemnation, Russia found itself increasingly isolated five days into its invasion while also facing unexpectedly fierce resistance on the ground in Ukraine and economic havoc at home.

For the second day in a row the Kremlin raised the spectre of nuclear war, announcing that its nuclear-capable intercontinental ballistic missiles, submarines and long-range bombers had all been put on high alert following President Vladimir Putin’s orders over the weekend.

Stepping up his rhetoric, Putin denounced the US and its allies as an “empire of lies”.

Meanwhile, people in Kyiv lined up for groceries after the end of a weekend curfew, standing beneath a building with a gaping hole blown in its side.

Messages aimed at the advancing Russian soldiers popped up on billboards, bus stops and electronic traffic signs across the capital. Some used profanity to encourage Russians to leave. Others appealed to their humanity.

“Russian soldier — Stop! Remember your family. Go home with a clean conscience,” one read.

Video footage from Kharkiv, meanwhile, showed residential areas being shelled, with apartment buildings shaken by repeated, powerful blasts. Flashes of fire could be seen and gray plumes of smoke.

Footage released by the Government from Kharkiv depicted what appeared to be a home with water gushing from a pierced ceiling. What looked like an undetonated projectile was on the floor.

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

“They wanted to have a blitzkrieg, but it failed, so they act this way,” said 83-year-old Valentin Petrovich, who watched the shelling from his downtown apartment and gave just his first name and his Russian-style middle name out of fear for his safety.

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

Fighting raged in other towns and cities across the country. The strategic port city of Mariupol, on the Sea of Azov, is “hanging on”, said Zelenskyy adviser Oleksiy Arestovich. An oil depot was reportedly bombed in the eastern city of Sumy.

In the seaside resort town of Berdyansk, dozens of protesters chanted angrily in the main square against Russian occupiers, yelling at them to go home and singing the Ukrainian national anthem. They described the soldiers as exhausted young conscripts.