Ukrainian President Volodymyr Zelensky has said that Russian forces had begun the "battle of Donbas" after senior officials said Moscow had begun a new offensive push along most of Ukraine's eastern flank.
"We can now say that Russian forces have started the battle of the Donbas, for which they have long prepared," he said in a video address.
Ukraine's presidential chief of staff said that "the second phase of the war has started," referring to Russia's new assault.
"Believe in our army, it is very strong," chief of staff Andriy Yermak wrote on the Telegram messaging app, assuring Ukrainians that Ukraine's forces could hold off the offensive.
Driven back by Ukrainian resistance in the north, Moscow has refocused its ground offensive in the two eastern provinces known as the Donbas, while launching long-distance strikes at other targets, including the capital, Kyiv.
We need your consent to load this rte-player contentWe use rte-player to manage extra content that can set cookies on your device and collect data about your activity. Please review their details and accept them to load the content.Manage Preferences
"This morning, along almost the entire front line of Donetsk, Luhansk and Kharkiv regions, the occupiers attempted to break through our defences," Security Council Secretary Oleksiy Danilov said in televised comments.
"They began their attempt to start the active phase this morning," he said.
Russian strikes killed at least eight civilians in the embattled eastern Ukrainian regions of Donetsk and Lugansk, local authorities said.
Four died as they tried to escape the city of Kreminna which Russian forces captured earlier today, Lugansk regional governor Sergiy Gaiday said on Telegram.
Four other civilians died in Russian bombing in the neighbouring region of Donetsk around 20kms (12 miles) east of Kreminna, according to regional governor Pavlo Kyrylenko.
Seven civilians killed in western city of Lviv
Ukraine said a Russian missile attack killed seven people in Lviv today, the first civilian victims in the western city.
Maksym Kozytskyy, the governor of Lviv which lies 60km (40 miles) from the Polish border, said preliminary reports suggested there were four strikes, three on warehouses that were not in use by the military and another on a car service station.
"It was a barbaric strike at a service station, it's a completely civilian facility," he told a news conference.
Andriy Sadoviy, mayor of Lviv, said the youngest victim among the dead was aged 30. The blast also wounded 11 others and shattered windows of a hotel housing Ukrainians evacuated from elsewhere in the country, he added.
"Seven peaceful people had plans for life, but today their life stopped," the mayor said.
The regional governor of Kharkiv said that authorities were continuing the evacuation of people from two areas where they expect fighting to take place.
A man and a woman were killed in Kharkiv today when shells hit a playground near a residential building, the prosecutor's office said in a post on the Telegram messaging service.
Russia denies targeting civilians in what it calls a special operation to demilitarise Ukraine and eradicate what it calls dangerous nationalists. It rejects what Ukraine says is evidence of atrocities, saying Ukraine has staged them to undermine peace talks.
Western capitals and Kyiv accuse Russian President Vladimir Putin of unprovoked aggression.
The United States military expects to start training Ukrainians on using howitzer artillery in coming days, a senior US defence official said today.
Last week, US President Joe Biden announced an additional $800m in military assistance to Ukraine, expanding the aid to include heavy artillery ahead of the wider Russian assault in eastern Ukraine.
The official, speaking on condition of anonymity, said the howitzer training would take place outside Ukraine.
French President Emmanuel Macron said today that his dialogue with Mr Putin had stalled after mass killings were discovered in Ukraine.
Russia's defence ministry said it had hit hundreds of military targets in Ukraine overnight. It said air-launched missiles had destroyed 16 military facilities in the Kharkiv, Zaporizhzhia, Donetsk and Dnipropetrovsk regions and in the port of Mykolayiv, which are in south and east Ukraine.
It added that the Russian air force had launched strikes against 108 areas where Ukrainian forces were concentrated and Russian artillery struck 315 Ukrainian military targets.
Russia is trying to take full control of the southeastern port city of Mariupol, which has been besieged for weeks and which would be a huge strategic prize, linking territory held by pro-Russian separatists in the east with the Crimea region that Moscow annexed in 2014.
Major Serhiy Volyna, commander of Ukraine's 36th marine brigade which is still fighting in Mariupol, appealed for help in a letter to Pope Francis, saying women and children were trapped among fighters in the city's steel works.
"This is what hell looks like on earth ... It's time (for) help not just by prayers. Save our lives from satanic hands," the letter said, according to excerpts tweeted by Ukraine's ambassador to the Vatican.
No fewer than 1,000 civilians were hiding in underground shelters beneath the vast Azovstal steel plant, the city council said today.
Video and audio footage showed explosions rumbling and smoke rising from the steelworks, which contain myriad buildings, blast furnaces and rail tracks.
Russia's invasion has damaged or destroyed up to 30% of Ukraine's infrastructure at a cost of $100bn, a Ukrainian minister said, adding reconstruction could be achieved in two years using frozen Russian assets to help finance it.
The Office of the UN High Commissioner said today that the civilian death toll from the war in Ukraine had surpassed 2,000, reaching 2,072 as of midnight on 17 April from the start of the Russian invasion on 24 February.
About four million Ukrainians have fled the country.
