Ukrainians and Russians on Saturday marked Orthodox Christmas under the shadow of war, as fighting persisted despite Kremlin leader Vladimir Putin unilaterally ordering his forces to pause attacks.

Despite Putin's ceasefire order, war-scarred cities in eastern Ukraine saw no significant let-up in the fighting as AFP journalists in the town of Chasiv Yar south of the frontline city of Bakhmut heard heavy artillery fire throughout much of Saturday morning.

The Russian defence ministry insisted its forces were observing the ceasefire but also said that the army had repelled the Kyiv forces' attacks in eastern Ukraine and killed dozens of soldiers on Friday.

Ukrainian authorities said that three people were killed on Friday.

In Moscow, 70-year-old Putin cut a lonely figure as he stood by himself at a service at a Kremlin church, the Cathedral of the Annunciation, to mark Orthodox Christmas.

In Kyiv, hundreds of worshippers on Saturday attended a historic service at the 11th century Kyiv Pechersk Lavra as Metropolitan Epifaniy, head of the Orthodox Church of Ukraine, led a Christmas liturgy in the pro-Western country's most signifiant Orthodox monastery.

The service is expected to anger the Moscow Patriarchate. Located in the capital Kyiv, the monastery used to be the seat of a branch of the Ukrainian Orthodox Chuch that was previously under Moscow's jurisdiction but which severed ties after Russia invaded Ukraine in February.

Orthodox Christians observe Christmas on January 7.

'Truly historic event'

Ukrainian worshippers hailed the mass.

"We've waited for this shrine for a long time," Veronika Martyniuk told AFP outside the church.

"This is a truly historic event, which I think every Ukrainian has been waiting for. Especially after the beginning of Russia's full-scale invasion," said the 19-year-old head of a choir from the western city of Ivano-Frankivsk.

Yury Slugin, a 33-year-old serviceman, said it was "especially important" for him to see the Ukrainian language and the Ukrainian church return to the Lavra. "This is a huge step for Ukraine," he added.

"Unfortunately, I am not at home today, far from my family," Slugin added, expressing hope that he will celebrate Christmas with his loved ones next year.

Security was tight. Worshippers had their passports checked and had to walk through metal detectors.

In the battered town of Chasiv Yar in eastern Ukraine, worshippers gathered in the basement shelter of an apartment building rather than in their church down the street, wary of possible shelling.

The congregation numbered just nine, down from its pre-war total of 100, as many residents have fled to safer territory.

"It's unusual here. Today is my first time in the basement," said Zinaida Artyukhina, 62, the church's sole remaining choir member.

"Thank God we gathered at all."

In Russia and Ukraine, Orthodox Christianity is the dominant religion and used to be seen as one of the strongest bonds tying the two nations.

Ukrainians have now largely turned their backs on the Russian Orthodox Church whose head Patriarch Kirill has backed the invasion.

Even the Ukrainian Orthodox Church of the Moscow Patriarchate has sought to distance itself from Russia. But the branch has still come under pressure from Ukrainian authorities.

The security service last year raided the Lavra, which is a UNESCO World Heritage site, over suspected links to Russian agents.

The Orthodox Church of Ukraine was established in 2018. The Moscow Patriarchate does not recognise the new church.

'Fake ceasefire'

Presidential adviser Mykhailo Podolyak on Saturday called Moscow's ceasefire "fake" and accused Russian troops of firing along the entire contact line.

The general staff of Ukraine's armed forces said Russia launched one missile strike and fired 20 rounds from multiple rocket launchers over the past 24 hours.

In the eastern region of Donetsk, two people died and seven were wounded, while in the southern region of Kherson one person lost his life and another seven were injured Friday, said Kyrylo Tymoshenko, deputy head of Ukraine's presidency.

"Peaceful settlements in the region were attacked with artillery, anti-aircraft guns, mortars and tanks," said Yaroslav Yanushevych, the head of the Kherson regional administration.

Ukraine has dismissed the ceasefire -- due to last until the end of Saturday (2100 GMT) -- as a tactic by Russia to gain time to regroup its forces.

Putin's order to stop fighting came after Moscow suffered its worst loss of life yet, with Ukrainian strikes killing at least 89 troops in the eastern town of Makiivka.

In a message released by the Kremlin, Putin congratulated Orthodox Christians, saying the holiday inspired "good deeds and aspirations."

He also praised the Orthodox Church and said it was "supporting our soldiers taking part in a special military operation," using the Kremlin term for the offensive in Ukraine.

Patriarch Kirill has said that dying in Ukraine "washes away all sins".