Russia-Ukraine updates: 2 US veterans who joined Ukrainian forces missing

At least seven people were killed and 11 others, including a child, were injured Monday morning in missile strikes across the western Ukrainian city of Lviv, according to local officia;s.

Lviv Oblast Gov. Maksym Kozystkiy said at a press conference that Russian missiles struck four targets -- three Ukrainian military infrastructure facilities and a tire service shop -- all of which suffered significant damage.

In a statement via social media, Lviv Mayor Andriy Sadovyi described the missile strikes as "powerful," saying they damaged or destroyed about 40 cars. Emergency services were responding to the deadly blasts, according to Sadovyi.

ABC News was at the scene of the burning tire service shop on the outskirts of Lviv, where firefighters were trying to extinguish the flames.

The strike also shattered the windows of a nearby orphanage as well as a hotel, where Sadovyi said evacuated Ukrainians are sheltering.

Lviv, a strategic city close to Ukraine's border with Poland, has been considered a safe haven for Ukrainians fleeing the Russian invasion. The city has been largely spared from the relentless bombardment and heavy fighting seen across much of the country since Feb. 24.

-ABC News' Brian Hartman, Max Uzol and Yuri Zaliznyak

Mariupol has not yet fallen, despite Russia's demands that Ukrainian troops defending the besieged Ukrainian port city surrender, according to Ukrainian Prime Minister Denys Shmyhal.

"There [are] still our military forces, our soldiers, so they will fight until the end," Shmyhal told ABC News' George Stephanopoulos in an exclusive interview Sunday on "This Week."

Mariupol is a strategic city for Moscow because it would allow Russian forces in the south to connect with troops in eastern Ukraine's contested Donbas region. It would also give Moscow a key port.

Although Mariupol remains under the Ukrainian government's control, Shmyhal said the city's residents are suffering.

"They have no water, no food, no heat, no electricity," he said. "They ask all of our partners to support and help stop this humanitarian catastrophe."

-ABC News' Monica Dunn

Russian commanders in Mariupol "will be concerned by the time it is taking to subdue" the Ukrainian port city, the U.K. Ministry of Defense said Monday in an intelligence update.

"Concerted Ukrainian resistance has severely tested Russian forces and diverted men and materiel, slowing Russia's advance elsewhere," the ministry said.

Mariupol, a strategic port in eastern Ukraine's Donetsk Oblast, has been under heavy Russian bombardment since the start of the invasion on Feb. 24. Strong resistance from Ukrainian troops has prevented Russian forces from taking full control of the city.

Despite Russia's claims that it would not strike Ukrainian cities or threaten civilian lives, "the targeting of populated areas within Mariupol aligns with Russia's approach to Chechnya in 1999 and Syria in 2016," according to the ministry.

"The effort to capture Mariupol has come at significant cost to its residents," the ministry added. "Large areas of infrastructure have been destroyed whilst the population has suffered significant casualties."

The mayor of Kharkiv, Igor Terekhov, lashed out at Russia for continuing its onslaught on the city despite it being Orthodox Palm Sunday.

"Dear Kharkiv citizens, today is the 53rd day of war, the war in which we are defending our lives and honor fighting against the ruthless army of the aggressor," Terekhov said in a recorded address translated from Russian by The Associated Press.

"And also today is a big Orthodox holiday, Palm Sunday. But it looks like those who wear the letter Z do not have a cross on them," he added, referring to the omnipresent letter painted on Russian tanks.

Kharkiv, Ukraine's second-largest city and a key outpost in the country's east, has been under intense shelling for days. Several people were killed in attacks on Sunday.

"Even days that are sacred to Christians are no reason for the enemy to lessen bombardments on Kharkiv," Terekhov said.

The vast majority of people in both Russia and Ukraine are Orthodox Christians. Holy Week began on Sunday with Easter coming on April 24. Many in Ukraine, including Kharkiv, celebrated Palm Sunday in bomb-damaged churches or buildings without electricity.

"I congratulate you all, my fellow Kharkiv citizens, with Palm Sunday, and on the eve of the Holy Week, I want to wish fortitude to all of us," Terekhov said. "The enemy is testing our resolve, let us show them that Kharkiv citizens will not be broken or intimidated."