KYIV, UKRAINE -- The southern Ukrainian city of Kherson was subjected Sunday to numerous shelling attacks from Russian-occupied parts of the Kherson region, across the Dnieper River, local officials said.

The head of the Kherson city administration, Roman Mrochko, said two people died in the shelling attacks and several others were wounded.

Meanwhile, Russian military personnel marked Orthodox Christmas on Sunday.

In Ukraine's northeast Kharkiv region, a man was killed and two other civilians wounded in Russian shelling of the Kupiansk district Sunday, according to the Kharkiv Regional Prosecutor's Office. A child was among the wounded.

Air defences shot down 21 of 28 drones launched by Russia overnight, the Ukrainian Air Force said Sunday. Russia also launched three anti-aircraft missiles against Ukraine.

On an unannounced visit to the country this weekend, Japanese Foreign Minister Yoko Kamikawa pledged Japan's continued support for Ukraine. Speaking at a press conference with Ukrainian Foreign Minister Dmytro Kuleba in Kyiv on Sunday, she said Japan had decided to contribute US$37 million to the NATO trust fund to provide drone detection systems, according to Japan's Foreign Ministry.

In Russia, more than 100 residents of the Russian border city of Belgorod have evacuated to an area farther away from Ukraine, local officials said.

"On behalf of the regional governor Vyacheslav Gladkov, we met the first Belgorod residents who decided to move to the safest place. More than 100 people were placed in our temporary accommodation centres," Andrey Chesnokov, head of the Stary Oskol district, some 115 kilometres (71 miles) from Belgorod, wrote on Telegram.

Ukrainian attacks on Belgorod on Dec. 30 killed 25 people, officials there said, with rocket and drone attacks continuing throughout this week.

Russian soldiers celebrated Orthodox Christmas on the front line with military priests leading prayer services both on Sunday and on Christmas Eve night, Russia's Defence Ministry said.

Russian President Vladimir Putin was joined by families of military personnel who died in the war in Ukraine at Christmas Eve services at his Novo-Ogaryovo residence, in the western suburbs of Moscow.

"Many of our men, our courageous, heroic guys, are warriors of Russia even now, during the holiday -- with arms in hand, they defend the interests of our country," he said to the attending families, according to the Kremlin's press service.

In his annual Christmas interview, carried by Russian state news agency TASS, Patriarch Kirill, leader of the Russian Orthodox Church, made reference to the war in Ukraine.

"The trials that befall us today ... are not capable of crushing our worldview, which directly includes love for the Motherland and readiness to defend it," he said, when asked how to reassure Russians in the midst of military and civilian deaths.

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Morton contributed from London.