Reinforced Russian troops backed by airstrikes pummelled a portion of eastern Ukraine on Saturday, blowing up bridges and shelling apartment buildings as they fought to capture two cities that would put a contested province under Moscow's control, Ukrainian officials said.

Russian and Ukrainian forces battled street-by-street in Sievierodonetsk and neighbouring Lysychansk, regional governor Serhiy Haidai said. Russian strikes killed four people, including a mother and child, in the nearby village of Hirske, Haidai said.

The cities are the last major areas of Luhansk province still held by Ukraine. The Russian attacks are central to the Kremlin's reduced wartime goal of seizing the entire Donbas region, where Moscow-backed separatists have fought Ukrainian forces for eight years and established self-proclaimed republics.

Russia also escalated attacks in Donestk, the other province that makes up the Donbas, the Ukrainian military said as the war reached its 101st day. Reflecting the close combat, Russian and Ukrainian military officers blamed each other for a fire that destroyed the main church at the Sviatohirsk monastery, one of Ukraine's holiest Orthodox Christian sites.

In recent days, the Russians focused on capturing Sievierodonetsk, which had a prewar population of about 100,000. At one point, they held 90% of the city, but Ukrainian soldiers clawed back some ground, Haidai reported Friday.

Western military analysts said Russia was devoting significant troop strength and firepower to what British officials described as a “creeping advance” in the Donbas.

“The combined use of air and artillery strikes has been a key factor in Russia's recent tactical successes in the region,” the U.K. Ministry of Defense said in a Saturday assessment.

The British ministry warned that after launching so many guided missiles, Russia was employing unguided missiles that have “almost certainly caused substantial collateral damage and civilian casualties.”

The Ukrainian military staff reported that Ukrainian forces repulsed nine attacks in the Donbas over 24 hours.

The claim could not be independently verified. While Russian forces are concentrated on seizing the Donbas in the east, Ukrainian troops have staged counterattacks to try to regain territory in their country's south.

After seizing most of the Kherson and Dnipropetrovsk regions, as well as the port city of Mariupol, Moscow has installed local administrators, offered residents Russian passports and taken other steps to consolidate its hold on occupied areas.

Russian shelling killed at least three civilians in the Black Sea port city of Mykolaiv, Mayor Oleksandr Senkevich said Saturday.

The Institute for the Study of War, a Washington-based think tank, said Russian-installed officials and troops faced growing resistance among the local population and “an increase in partisan activity in southern Ukraine.”

The institute cited accounts on Russian Telegram channels of threats against locals who received Russian passports. The Ukrainian Centre for National Resistance, which established a website to advise residents on sabotage and other techniques, said Kherson residents were encouraged to burn down a Russian passport centre.

The Ukrainian military general staff noted with approval the trouble that Russian occupation authorities were encountering. It said Russian leaders in Kherson wore bulletproof vests and traveled in armored vehicles.

In other developments:

— Ukraine's foreign minister denounced France's president for saying the West shouldn't “humiliate” Russian President Vladimir Putin. French President Emmanuel Macron said in an interview with regional French newspapers Friday that Putin made a “historic error” in invading Ukraine but world powers shouldn't "humiliate Russia, so that when the fighting stops, we can build a way out together via diplomatic paths.”

Ukrainian Foreign Minister Dmytro Kuleba tweeted in response: “Calls to avoid humiliation of Russia can only humiliate France and every other country that would call for it. ... We all better focus on how to put Russia in its place. This will bring peace and save lives.”

— The bodies of more than 1,300 civilians have been exhumed so far in the region around Ukraine's capital following Russia's military retreat from around Kyiv, Ukraine's Interior Ministry reported Saturday.

The bodies were sent to morgues for forensic examination, and some 200 of the victims have not been identified, ministry spokeswoman Alyona Matveyeva said.

Since Russia's withdrawal from the Kyiv region in early April, Ukrainian authorities have been collecting the dead, exhuming bodies from mass graves and working to document the killings and collect evidence for eventual war crimes investigations and possible prosecutions.

— A Russian rocket hit an agricultural site Saturday in the Odesa region, wounding two people, according to a regional military chief. A Russian Defense Ministry spokesman said a missile attack destroyed a base of foreign mercenaries.

Odesa is home to Ukraine's largest seaport and therefore vital to the country's ability to ship grain and other commodities.

The rocket attack came hours after Kuleba, the foreign minister, tweeted: “Ukraine is ready to create necessary conditions to resume exports from the port of Odesa. The question is how to make sure that Russia doesn't abuse the trade route to attack the city."

— Ukrainian presidential adviser Mykhailo Podolyak said in an interview published Saturday that Russia is suffering significantly fewer military casualties compared to the first six weeks of the war.

The lower figures might make Russian commanders “think that they are fighting successfully,” the website Meduza quoted Podolyak as saying. Speaking on Ukrainian television, he expressed optimism that new Western-supplied weaponry could change the “mathematics” of the war.

—- Pope Francis says he needs he needs to wait for the “right moment” to go to Ukraine.

A Ukrainian refugee who was in a group of children visiting the Vatican asked the pontiff if he would go to his homeland. Francis told the boy he thinks a lot about the children in Ukraine and has a desire to go there. He said it's “not easy to take a decision that could do more harm to all the world than good. I must find the right moment to do it.”

The pope said he would discuss the issue next week when some Ukrainian government representatives visit the Vatican.