Russian military vehicles move on a highway in an area controlled by Russian-backed separatist forces near Mariupol, Ukraine, Monday, April 18, 2022. Mariupol, a strategic port on the Sea of Azov, has been besieged by Russian troops and forces from self-proclaimed separatist areas in eastern Ukraine for more than six weeks. (AP Photo/Alexei Alexandrov)

Russia's military has 76 combat battalions in eastern and southern Ukraine, a rise from a week ago, a senior U.S. defense official said.

The new figure is up from 65 last week, which could translate to around 50,000 to 60,000 troops, the Pentagon said.

The Associated Press contributed to this report.

Volunteer Silas Breen, below left, from the Calvary Bible Institute, prays with David, from Ukraine, at San Diego Calvary's shelter for Ukrainians arriving after crossing into the United States from Tijuana, Mexico on April 1, 2022, in Chula Vista, Calif. (AP Photo/Gregory Bull)

Border officials in March detained more than 5,000 Ukrainians seeking refuge in the United States, according to U.S. Customs and Border Protection figures released Monday. 

The number is a sharp increase from the 1,150 Ukrainian migrants encountered by CBP in February as Russia continues its invasion of its neighbor to the west that began on Feb. 24. 

All told, the figures are part of more than 220,000 detentions in March, the highest monthly total since 2000. Many Ukrainians will receive border protections after the Biden administration announced Monday that they will be eligible for Temporary Protected Status in the U.S. 

Ukrainians who arrived by April 11 can apply for 18 months of protection from being deported, according to the announcement. 

A resident looks at a damaged apartment building in Mariupol, Ukraine, on Saturday. (AP/Alexei Alexandrov)

A Ukraine Marine commander who is trying to defend Mariupol has written a letter to Pope Francis pleading for help, declaring that the besieged city "is what hell on earth looks like." 

The desperate message from Maj. Serhiy Volyna of the 36th Separate Marine Brigade was published Monday by the Ukrainska Pravda newspaper. 

"You have probably seen a lot in your life. But I am sure that you have never seen the things that are happening to Mariupol," Volyna wrote. "Because this is what hell on earth looks like." 

For more on this story: Ukraine Marine commander tells Pope Mariupol is 'what hell on earth looks like'

Rear Admiral Oleksiy Neizhpapa, commander of the Ukrainian Naval Forces, speaks during the opening ceremony for the Sea Breeze multinational maritime exercise in the Kherson Region of Ukraine in June 2021. (Press service of the Ukrainian Naval Forces/Handout via REUTERS)

The head of Ukraine’s Navy has received a promotion following the sinking of Russia's Moskva warship last week in what officials are hailing as a "brilliant operation." 

Rear Admiral Oleksiy Neizhpapa has been elevated to the rank of Vice Admiral, according to a statement from Ukrainian President Volodymyr Zelenskyy’s office.  

A U.S. official had told Fox News on Friday that the latest assessment by the U.S. is that the Moskva was struck by two Ukrainian missiles before it sank.

For more on this story: Ukraine Navy chief promoted by Zelenskyy after sinking of Russian warship

Retired Navy Commander Kirk S. Lippold joined 'Fox & Friends' to discuss the latest on the Russian invasion into Ukraine.

Emergency workers clear up debris after an airstrike hit a tire shop in the western city of Lviv, Ukraine, on Monday. (AP/Philip Crowther)

Lviv’s mayor told Fox News Monday that the western Ukrainian city "must be ready" for further attacks from the Russian military after a series of fresh airstrikes there reportedly left at least 7 people dead. 

The deaths are the first to occur inside the city since Russia launched its invasion on Feb. 24, Andriy Sadovyi also said. 

"We must be ready [for a] new Russian attack. And together we must maximum protect our country," Sadovyi told Fox News. "It is a very special moment in our life. We have only one country, we have only one land. I believe in our victory, never give up. Only victory."

For more on this story: Ukrainian mayor says city 'must be ready' for more Russian attacks after deadly airstrikes reported

Fox News’ Jeff Paul contributed to this report.

A Russian warship lays on the bottom of the Black Sea after Ukraine reportedly sank the Moskva with a pair of Neptune missiles last week.

The Defense Ministry shared additional information regarding how the ship was targeted in a new post.

At least seven people have been killed and 11 others were injured in Lviv, Ukraine, Monday morning, after Russia’s military launched several missiles into the city, officials said.

The missile attack in the Western city included at least four missiles which hit three warehouses and also struck a car tire service center, according to regional Governor Maksym Kozystkiy.

Lviv Mayor Andriy Sadovyi said the attack further proves that there are no safe places for civilians in Ukraine.

For more on the story: 7 dead, 11 injured after Russia's military launched missiles into Lviv

Ukraine has vowed to "fight absolutely to the end” to keep the port city of Mariupol from Russia's control, Ukrainian Prime Minister Denys Shmyhal said.

Russia's military has continued its seemingly relentless siege of Mariupol, which the city has resisted for seven days, as it seeks its biggest victory of the war.

A few thousand Ukrainian fighters reportedly remain in the city.

Capturing Mariupol would provide Russia with direct access to the Sea of Azov, giving it routes to resupply and reignite its offensive strategy in Ukraine, specifically in the eastern Donbas region. It would also provide Russia a land corridor to the Crimean Peninsula, an area it seized from Ukraine in 2014.

During a nightly address Sunday, Ukrainian President Volodymyr Zelenskyy said his administration and military were “doing everything to ensure the defense” of eastern Ukraine.

The Associated Press contributed to this report.

Ukrainian Prime Minister Denys Shmyhal said during an interview on Sunday that the Ukrainian port city of Mariupol had still not fallen into Russian control.

"The city still has not fallen," Shmyhal said during a segment on ABC's "This Week."

"There is no whole control," he added via Reuters, noting armies on both sides were continuing to fight.

The Ukrainian government was continuing to provide humanitarian aid to civilians in the city.

"We need more money for executing of our humanitarian and social obligations," Shmyhal said. "Now, only half of our economy is working. So we ask for financial support."

Ukrainian fighters who were holed up at the Azovstal steel mill in the last known pocket of resistance inside Mariupol ignored Russia’s surrender-or-die ultimatum on Sunday and held out against the capture of the strategically vital port.

Moscow gave the defenders a midday deadline to surrender, saying those who laid down their arms were "guaranteed to keep their lives." The Ukrainians rejected it, just as they've done with previous ultimatums.

The relentless bombardment and street fighting in Mariupol have killed at least 21,000 people, by the Ukrainians' estimate. A maternity hospital was hit by a lethal Russian airstrike in the opening weeks of the war, and about 300 people were reported killed in the bombing of a theater where civilians were taking shelter.

An estimated 100,000 remained in the city out of a prewar population of 450,000, trapped without food, water, heat or electricity in a siege that has made Mariupol the scene of some of the worst suffering of the war.

The Associated Press contributed to this report. 

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