Pope Francis on Wednesday urged people to spend less on Christmas celebrations and gifts this year and send the difference to Ukrainians to help them get through the hunger and cold of winter.

The pope, who has been making appeals for Ukraine at nearly every public event since Russia invaded its neighbour in February, made the unscripted plea at the end of his weekly general audience.

"Brothers and sisters, I tell you, there is so much suffering in Ukraine, so much, so much," he said, adding that he wanted to draw attention to the particular problems Ukrainians will bear in the coming months.

"It is beautiful to celebrate Christmas, but let us lower the level of Christmas spending. Let's have a more humble Christmas, with more humble gifts, and send what we save to the Ukrainian people, who need it," he said, prompting several rounds of applause in the audience hall.

"They are suffering so much, they are going hungry, they feel the cold and many are dying because there are not enough doctors and nurses available," he said.

He spoke as millions of civilians enduring Europe's biggest conflict since World War Two have had to contend with cuts to power, heat and water caused by Russian attacks on infrastructure as sub-zero temperatures take hold.

"Let's not forget. Christmas, yes. In peace with the Lord, yes. But with Ukrainians in our hearts. Let's make this concrete gesture for them," he said.

Francis spoke on the same day the Ukrainian national church in Rome, Santa Sofia, issued a new appeal to Italians to donate clothing and medicine that volunteers have been taking to Ukraine by the truck load since March.