Multiple blasts rock western Ukraine city of Lviv

Multiple explosions apparently caused by missiles struck the western Ukrainian city of Lviv early Monday as the country was bracing for an all-out Russian assault in the east. At least six people were killed in the city, which has been spared much of the worst violence in almost two months of war.

Ukrainian President Volodymyr Zelensky vowed to "fight absolutely to the end" in strategically vital Mariupol, meanwhile, where the ruined southeastern port city's last known pocket of resistance was holed up in a sprawling steel plant laced with tunnels.

Plumes of thick, black smoke were rising over Lviv after the explosions, which were witnessed by Associated Press staff. Lviv and the rest of western Ukraine have not been immune but have been less affected by the fighting than other parts of the country and have been considered a relative haven.

Lviv's regional governor, Maksym Kozytskyy, said six people were killed and another eight, including a child, were wounded by four Russian missile strikes. He said three hit military infrastructure facilities and one struck a tire shop. He said emergency teams were putting out fires caused by the strikes.

Lviv Mayor Andriy Sadovyi put the toll at six dead and 11 wounded, including one child.

Military analysts say Russia is increasing its strikes on weapons factories, railways and other infrastructure targets across Ukraine to wear down the country's ability to resist a major ground offensive in the Donbas, Ukraine's Russian-speaking eastern industrial heartland.

With missiles and rockets battering various parts of the country, Zelensky accused Russian soldiers of torture and kidnappings in areas they control.

The fall of Mariupol, which has been reduced to rubble in a seven-week siege, would give Moscow its biggest victory of the war. But a few thousand fighters, by Russia's estimate, were holding on to the giant, 11-square-kilometre Azovstal steel mill.

"We will fight absolutely to the end, to the win, in this war," Ukrainian Prime Minister Denys Shmyhal vowed Sunday on ABC's This Week. He said Ukraine is prepared to end the war through diplomacy if possible, "but we do not have intention to surrender."

Many Mariupol civilians, including children, are also sheltering at the Azovstal plant, Mikhail Vershinin, head of the city's patrol police, told Mariupol television. He said they are hiding from Russian shelling and from Russian soldiers.

Capturing the city on the Sea of Azov would free Russian troops for a new offensive to take control of the Donbas region in Ukraine's industrial east. Russia also would fully secure a land corridor to the Crimean Peninsula, which it seized from Ukraine in 2014, and it would deprive Ukraine of a major port and prized industrial assets.

Russia is bent on capturing the Donbas, where Moscow-backed separatists already control some territory, after its attempt to take the capital, Kyiv, failed.

"We are doing everything to ensure the defence" of eastern Ukraine, Zelensky said in his nightly address to the nation.

As for besieged Mariupol, there appeared to be little hope of military rescue. Foreign Minister Dmytro Kuleba told CBS's Face the Nation on Sunday that the remaining Ukrainian troops and civilians there are basically encircled. He said they "continue their struggle," but that the city effectively doesn't exist anymore because of massive destruction.