(AFP) - Ukrainians and Russians marked Orthodox Christmas on Saturday, as the 36-hour ceasefire ordered by Russian President Vladimir Putin ran its course with little sign the fighting had eased.

War-scarred cities in eastern Ukraine saw no significant let-up in the combat. 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 unilateral ceasefire, which ended at 11:00 pm in Kyiv (2100 GMT). But they also said they had repelled attacks in eastern Ukraine and killed dozens of Ukrainian soldiers Friday.

Ukrainian authorities said only three people had been killed on Friday.

In Moscow, the 70-year-old Putin stood alone at a service at a Kremlin church, the Cathedral of the Annunciation, to mark Orthodox Christmas.

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

President Volodymyr Zelensky, in his evening address, said he was happy to see so many people attend the service on a day that "has already become historic for Ukraine, for the spiritual independence of our people".

On the Orthodox Holy Day, "the world was once again able to see how false any words of any level coming from Moscow are," he added.

"They said something about an alleged ceasefire... But the reality is Russian shells that again hit Bakhmut and other Ukrainian positions."

Ukraine had previously 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 days after Moscow suffered its heaviest casualties in a single attack yet, with Ukrainian strikes killing at least 89 troops in the eastern town of Makiivka.

- 'Truly historic event' -

Ukrainian worshippers hailed the Kyiv 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.

Security was tight: Worshippers had their passports checked and entered through metal detectors.

In the battered town of Chasiv Yar in eastern Ukraine, worshippers gathered in the basement shelter of an apartment building instead of 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.

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

The Ukrainian Church was previously under Moscow's jurisdiction but severed ties after Russia launched its invasion last February.

Ordinary Ukrainians have also largely turned their backs on the Russian Orthodox Church, whose leader Patriarch Kirill has backed the invasion.

The Orthodox Church of Ukraine was established in 2018 but remains unrecognised by the Moscow Patriarchate.

- 'Fake ceasefire' -

Presidential adviser Mykhailo Podolyak on Saturday accused Russian troops of firing along the entire contact line despite the announced ceasefire.

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

Two people died and seven were wounded in the eastern region of Donetsk, while in the southern region of Kherson one person was killed 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.

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 for "supporting our soldiers taking part in a special military operation", using the Kremlin term for the offensive in Ukraine.

Meanwhile the British government announced it would host a meeting of justice ministers in March to discuss ways to support the International Criminal Court's investigation of alleged war crimes in Ukraine.

In December ICC prosecutor Karim Khan, who will attend the March conference, urged the international community to support and fund it.

"We need the tools to do the job," he said. "We do not have those tools."

© Agence France-Presse