LVIV/KYIV (AFP, REUTERS) - Authorities reported multiple explosions in western and southern Ukraine on Monday (April 18), including in the western city of Lviv which has so far been spared much of the fighting since Russia invaded the country.

Authorities in Lviv said a series of "powerful" Russian missiles on military infrastructure hit the city and left several dead and ignited blazes. 

A Lviv resident told AFP they could see thick clouds of grey smoke in the sky above residential buildings and air raid sirens sounded throughout the city during and after the strikes. 

“At the moment, we are able to confirm that seven are dead and 11 injured. A child was among the victims,” the Lviv regional governor Maksym Kozytsky said on social media.

"Three victims are in critical condition," he added.

He said that four Russian missiles had targeted Ukrainian military infrastructure and that a car tyre centre had also been struck.

“Fires were set off as a result of the strikes. They are still being put out. The facilities were severely damaged,” Kozytsky said.

Twenty-one-year-old Lviv resident Andrei said he was sleeping when the sirens began wailing at around 8am (2pm Singapore time).

“I slept through the first three strikes, but then when the last one hit, it was like my windows were about to break, and the furniture moved,” he told AFP.

The strikes in Lviv come as Russian forces have over recent days been intensifying strikes on the capital Kyiv further east, targeting several facilities that produce military hardware. 

“Five powerful missile strikes at once on the civilian infrastructure of the old European city of Lviv,” Ukrainian presidential aide Mykhaylo Podolyak wrote on Twitter earlier.

“The Russians continue barbarically attacking Ukrainian cities from the air, cynically declaring to the whole world their ‘right’ to kill Ukrainians,” he added.

Lviv, near Ukraine’s border with Poland, so far been spared being embroiled in the worst of the fighting sparked by Russia’s invasion of its pro-Western neighbour nearly two months ago.

The city instead has become of refuge for people displaced from the war-scarred east and at the start of the fighting hosted several Western embassies transferred from Kyiv.

Lviv in late March was hit by a series of Russian strikes that targeted a fuel depot and injured five people. On March 18, bombardments hit an aircraft repair factory near Lviv’s airport. No injuries were reported.

Russian cruise missiles on March 13 targeted a major military base about 40km north-west of Lviv, killing at least 35 people and injuring 134.

In the Ukrainian capital, a Reuters reporter heard a series of blasts on the left bank of the Dnipro river. Local authorities were yet to provide any official information on their cause.  

After failing to overcome Ukrainian resistance in the north, the Russian military has refocused its ground offensive on the Donbass region, while launching long-distance strikes at targets elsewhere, including the capital, Kyiv. 

On Monday, Russia said it launched mass strikes overnight on the Ukrainian military and associated military targets, using its air force, missile forces, artillery and air defence systems to hit hundreds of targets.

The Russian defence ministry said in a statement that air-launched missiles had destroyed 16 Ukrainian military facilities overnight, including five command posts, a fuel depot and three ammunition warehouses, as well as Ukrainian armour and forces.

It said those strikes took place in the Kharkiv, Zaporizhzhia, Donetsk and Dnipropetrovsk regions and in the port of Mykolayiv, and that the Russian air force had launched strikes against 108 areas where it said Ukrainian forces and armour were concentrated.

In other areas, the defence ministry spoke of destroying 12 Ukrainian strike drones and tanks and of using Iskander missiles to destroy four arms and equipment depots in the Luhansk, Vinnytsia and Donetsk regions.

The defence ministry said Russian artillery had also struck 315 Ukrainian military targets overnight and that air defence systems had been used to bring down three Ukrainian army helicopters, two MiG-29 fighters and one SU-25 plane.

According to Ukrainian media outlet Suspilne, two people were wounded in attacks in the southern region of Dnipropetrovsk.

Eighteen people have been killed and more than 100 wounded in shelling in the past four days in the north-eastern city of Kharkiv, Ukraine's President Volodymyr Zelensky said.

"This is nothing but deliberate terror: mortars, artillery against ordinary residential quarters, against ordinary civilians," he said late on Sunday (April 17).

Russia denies targeting civilians and has rejected what Ukraine says is evidence of atrocities as staged to undermine peace talks. It calls its action a special military operation to demilitarise Ukraine and eradicate what it calls dangerous nationalists.

The West and Kyiv accuse Russian President Vladimir Putin of unprovoked aggression.

Ukrainian Prime Minister Denys Shmyhal said troops in the pulverised port of Mariupol were still fighting on Sunday, despite a Russian demand to surrender by dawn.

"The city still has not fallen," he told ABC's "This Week" programme, adding that Ukrainian soldiers continued to control some parts of the southeastern city.

On Saturday, Russia said it had control of urban areas, with some Ukrainian fighters remaining in the Azovstal steelworks overlooking the Sea of Azov.

Capturing Mariupol, the main port in the Donbass region, would be a strategic prize for Russia, connecting territory held by pro-Russian separatists in the east with the Crimea region that Moscow annexed in 2014.

On the streets of Mariupol, small groups of bodies were lined up under colourful blankets, surrounded by destroyed trees and scorched buildings.

Residents, some pushing bicycles, picked their way around destroyed tanks and civilian vehicles while Russian soldiers checked the documents of motorists.

Among them was Irina, who was evacuating with a niece wounded in the shelling.

"I have a daughter in DNR," she said, referring to the self-proclaimed Donetsk People's Republic. "Maybe we will try to move there for the time being.

"I hope they will re-build (Mariupol). The most important thing is utility systems. Summer will pass fast and in winter it will be hard."

Mr Serhiy Gaidai, the governor of the Luhansk region, reported street fighting between Ukrainian and Russian troops had begun and he repeated a plea for people to evacuate. 

"The next week will be difficult," he said in an earlier post on his Facebook page. "It may be the last time we have a chance to save you."

About four million Ukrainians have fled the country, cities have been shattered and thousands have died since the start of the invasion on Feb 24.

The economic damage is significant. Mr Shmyhal said Ukraine's budget deficit was about US$5 billion (S$6.79 billion) a month and urged Western governments for more financial aid.

On Twitter, Mr Zelensky said he had discussed ensuring Ukraine's financial stability and preparations for post-war reconstruction with International Monetary Fund Managing Director Kristalina Georgieva, quoting her as having said support was essential to lay the foundations for rebuilding.

Ukraine pressed on with efforts to swiftly join the European Union, as officials completed a questionnaire that is a starting point for the EU to decide on its membership.