Russia-Ukraine updates: Russian missiles hit close to nuclear reactors: IAEA director

Russian President Vladimir Putin celebrated the Russian seizure of Lysychansk and the majority of the Luhansk regional border in eastern Ukraine by appearing to direct his military to conduct an “operational pause”, the Institute for the Study of War reported on Monday.

Putin and Russian Defense Minister Sergey Shoigu called the recent Russian gains in the Luhansk region as a major victory for Russian forces in Ukraine.

The Russian president also stated that the Russian units that participated in the battle for Lysychansk should rest to increase their combat capabilities, the ISW report claimed.

Putin‘s public comment was likely meant to signal his concern for the welfare of his troops in the face of periodic complaints in Russia about the treatment of Russian soldiers, the ISW experts said.

Russian troops that fought through the Luhansk region are very likely in need of a significant period in which to rest and refit before resuming large-scale offensive operations, observers noted.

It is not clear, however, that the Russian military will accept the risks associated with a long enough operational pause to allow these likely exhausted forces to regain their strength, the ISW report said.

Putin was quick to remark on Monday that “other military formations, including the East Group and the West Group, must carry out their tasks according to the previously approved plans.”

“I hope that everything will happen … in the same way as it has happened in Luhansk,” the Russian President added as quoted by local media.

Vyacheslav Volodin, who chairs the Russian Duma -- the lower house of the Federal Assembly -- said on Tuesday that Ukraine was "doing everything" to ensure that Moscow's troops would not stop their "special military operation" at the borders of the self-proclaimed Donetsk People's Republic and Luhansk People's Republic in eastern Ukraine, according to Russian state media.

Serhii Haidai, the head of the Luhansk Regional Military Administration, said on Tuesday that Russian attacks in the Luhansk region destroyed more than 90% of the infrastructure in the territories that were actively defended by the Ukrainian military.

An overwhelming majority of houses were under fire, Haidai said, and most of them “can't be restored.”

-ABC News' Edward Szekeres, Yuriy Zaliznyak, Max Uzol and Nataliia Kushnir

Russian forces will "now almost certainly" switch focus to capturing Donetsk Oblast after claiming control of neighboring Luhansk Oblast in eastern Ukraine's disputed Donbas region, according to intelligence briefings from the U.K. Ministry of Defense.

Russian President Vladimir Putin declared victory in Luhansk on Monday, a day after Ukrainian troops withdrew from the city of Lysychansk -- their last stronghold of resistance in the province. Ukrainian troops had spent weeks trying to defend Lysychansk and to keep it from falling to Russian forces, as the neighboring city of Sievierodonetsk did a week ago. A river separates the two cities.

"Russia's focus will now almost certainly switch to capturing Donetsk Oblast, a large portion of which remain under the control of Ukrainian forces," the U.K. Ministry of Defense said in Monday's briefing. "The fight for the Donbas has been grinding and attritional and this is highly unlikely to change in the coming weeks."

Putin has made capturing the entire Donbas -- Ukraine's mostly Russian-speaking industrial heartland in the east -- a key goal in his war in neighboring Ukraine. Russia-backed separatists in Donbas have battled Ukrainian forces since 2014, when they declared independence from Kyiv after the Russian annexation of Ukraine's Crimean Peninsula. Moscow formally recognized the self-proclaimed republics in Luhansk and Donetsk oblasts just days before launching its Feb. 24 invasion.

"Russia's relatively rapid capture of Lysychansk extends its control across virtually all of the territory of Luhansk Oblast, allowing it to claim substantive progress against the policy objective it presented as the immediate purpose of the war, namely 'liberating' the Donbas," the U.K. Ministry of Defense said in Tuesday's briefing.

"Ukrainian forces have likely largely withdrawn in good order, in line with existing plans," the ministry continued. "The Ukrainian held areas of Sieverodonetsk-Lyschansk consisted of a bulge or salient which Russian could attack from three sides. There is a realistic possibility that Ukrainian forces will now be able to fall back to a more readily defendable, straightened front line."

"The battle for the Donbas has been characterised by slow rates of advance and Russia’s massed employment of artillery, levelling towns and cities in the process," the ministry added. "The fighting in Donetsk Oblast will almost certainly continue in this manner."

Speaking of the situation in Ukraine in an exclusive interview with Reuters over the weekend, Pope Francis said he might be heading to Ukraine after returning from his trip to Canada.

Francis, who has repeatedly condemned Russia's invasion of Ukraine, said he “would like to go [to Ukraine],” but wanted to “go to Moscow first."

No pope has ever visited Moscow. Last Thursday, Francis implicitly accused Russia of waging a "cruel and senseless war of aggression."

Francis noted over the weekend that there have been contacts between Vatican Secretary of State Cardinal Pietro Parolin and Russian Foreign Minister Sergei Lavrov about a possible trip to Moscow.

“After I come back from Canada, it is possible that I will manage to go to Ukraine," Francis said. "The first thing is to go to Russia to try to help in some way, but I would like to go to both capitals."

According to Francis, the Vatican first inquired about a trip to Russia several months ago, but Moscow said it was not the right time.

-ABC News' Edward Szekeres, Yuriy Zaliznyak, Max Uzol and Fidel Pavlenko

Ukraine spends almost as much on its army in a month as it did in a year before Russia's invasion, Ukrainian Prime Minister Denys Shmyhal told local media on Sunday.

Ukraine's monthly military budget is now about $4.4 billion, according to Shmyhal. Before the war, its annual military budget was close to $5.3 billion, the prime minister said.

Shmyhal added that Ukraine's overall monthly budget is lacking around $150 million. Many businesses have suspended work or completely ceased to exist, he said, adding that millions of tons of harvest remain stuck in warehouses due to Russia blocking the path for exports.

On Sunday, Turkish customs detained a Russian cargo ship with grain stolen by Russian forces and shipped from the Ukrainian port of Berdyansk, the Ukrainian ambassador to Turkey said.

Turkish President Recep Tayyip Erdogan said Friday that Turkey will be able to re-export grain products, including wheat, oat, and barley from the Black Sea to countries in need after talks with Russia and Ukraine that will be held in the coming days.

Turkey has about 20 bulker ships ready to transport grain, Erdogan added.

-ABC News' Edward Szekeres, Yuriy Zaliznyak, Max Uzol and Fidel Pavlenko