Russia warned Kyiv residents to flee their homes on Tuesday and rained rockets on the city of Kharkiv as Russian commanders intensified their bombardment of Ukrainian urban areas in a shift of tactics after their six-day assault stalled.

A US official said a 64-km-long armoured column bearing down on the capital Kyiv had not made any advances in the past 24 hours, frozen in place by logistics problems, short on fuel and food, and perhaps pausing to reassess tactics.

Russia’s defence ministry said its forces would strike targets in Kyiv used by Ukraine’s security service and also communications sites.

It warned residents near such sites to leave their homes, while giving no information about where in the city of three million people those targets were located.

Speaking in a heavily guarded government compound in Kyiv, President Volodymyr Zelensky said Russia must “first stop bombing people” before peace talks could make any headway.

In a joint interview with Reuters and CNN, Zelensky also urged Nato members to impose a no-fly zone to stop Russia’s air force, something the military alliance has ruled out.

As Zelensky, unshaven and wearing simple khaki clothes, spoke, news came that a Russian missile had struck a TV tower near a Holocaust memorial site in Kyiv, killing five people.

Rocket strikes on Ukraine’s second biggest city Kharkiv killed at least 10 people and wounded 35, Ukrainian interior ministry adviser Anton Herashchenko said.

Similar strikes had killed and wounded dozens in Kharkiv on Monday.

Zelensky, who also spoke over phone for 30 minutes with US President Joe Biden on Tuesday, said the artillery barrages on Kharkiv, a city of 1.5 million, amounted to “state terrorism”.