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

Humanitarian corridors to evacuate civilians will not reopen in eastern Ukraine on Monday due to continuous bombardment from Russian forces, according to Ukrainian Deputy Prime Minister Iryna Vereshchuk.

"In violation of international humanitarian law, Russian occupiers do not stop blocking and shelling humanitarian routes," Vereshchuk said in a statement via social media on Monday. "Therefore, for safety reasons, a decision was made today not to open humanitarian corridors. We will make all our efforts to make the humanitarian corridors work again as soon as possible."

Russian missiles destroyed 16 Ukrainian military facilities overnight, including five command headquarters, a fuel depot and three ammunition depots, as well as concentrations of Ukrainian military "personnel and equipment" in several areas of eastern Ukraine, according the Russian Ministry of Defense.

The Ukrainian deputy premier issued an appeal to Russian leadership, urging that evacuation routes for civilians be allowed to open from Mariupol, a hard-hit port city in the besieged Donetsk Oblast, to Berdyansk, a port city in the Zaporizhzhia Oblast. She also demanded an "urgent humanitarian corridor" for civilians, including women and children, who are sheltering in the territory of the Azovstal iron and steelworks plant in Mariupol.

"Your refusal to open these humanitarian corridors will in the future be a basis for bringing all involved to prosecute for war crimes," Vereshchuk said.

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."