In a post on Twitter, Zelensky said he told the Pope of the "difficult humanitarian situation" and how rescue corridors were being blocked by Russian troops.

Zelensky added: "The mediating role of the Holy See [the jurisdiction of the Pope] in ending human suffering would be appreciated."

It comes after Zelensky said on Monday that Jerusalem could potentially be a location for future top-level peace talks between Ukraine and Moscow.

Ukraine retakes key Kyiv suburb

Ukraine said it retook a strategically important suburb of Kyiv early Tuesday, as Russian forces squeezed other areas near the capital and their attack on the embattled southern port of Mariupol raged unabated.

Explosions and bursts of gunfire shook Kyiv, and black smoke rose from a spot in the north. Intensified artillery fire could be heard from the northwest, where Russia has sought to encircle and capture several suburban areas of the capital, a crucial target.

Residents sheltered at home or underground under a 35-hour curfew imposed by city authorities that runs to Wednesday morning.

Russian forces also pressed their siege of Mariupol after the southern port city’s defenders refused demands to surrender, with fleeing civilians describing relentless bombardments and corpses lying in the streets. But the Kremlin’s ground offensive in other parts of the country advanced slowly or not at all, knocked back by lethal hit-and-run attacks by the Ukrainians.