Ukrainian President Volodymyr Zelensky has said the weapons that Kyiv had asked for were finally being delivered by allies.
The arms would help save the lives of thousands of people, he added.
In a late night video address, Mr Zelensky also said comments earlier in the day by a Russian commander about the need to linkup with Moldova showed Moscow wanted to invade other countries.
A Russian general said that Moscow wants to take full control over southern Ukraine, a statement Ukraine said gave the lie to Russia's previous assertions that it had no territorial ambitions.
Rustam Minnekayev, deputy commander of Russia's central military district, was quoted by Russian state news agencies as saying full control over southern Ukraine would give it access to a breakaway, Russian-occupied part of Moldova in the west.
That would cut off Ukraine's entire coastline and mean pushing hundreds of miles west beyond current lines, past the major Ukrainian cities of Mykolaiv and Odessa.
Moscow says it is conducting a "special military operation" to demilitarise Ukraine and liberate its population from people it calls dangerous nationalists.
Ukraine and its Western allies call Russia's invasion an unjustified war of aggression.
"They stopped hiding it," Ukraine's defence ministry said on Twitter.
Russia had "acknowledged that the goal of the 'second phase' of the war is not victory over the mythical Nazis, but simply the occupation of eastern and southern Ukraine. Imperialism as it is."
Kremlin spokesman Dmitry Peskov declined to comment when asked if Russia had expanded the goals of its operation and how Moscow saw the political future of southern Ukraine.
A senior EU official said the next couple of weeks were likely to be decisive.
"This is not a fairy tale with an imminent happy ending. I think we are likely to see a very significant increase in the intensity of Russian military attacks in the east, I think we are likely to see an intensification of Russian military attacks along the coast," the official told reporters.
Ukraine's general staff said Russian forces had increased attacks all along the frontline in the east and were trying to mount an offensive in the Kharkiv region, north of their main target, the Donbas.
Russia's defence ministry said its forces had captured a large arms depot in the Kharkiv region.
It also reported hitting dozens of targets in the Donetsk and Kharkiv regions today.
In Kharkiv city, Russian shellfire hit the main Barabashovo market.
Ambulance services said there had been casualties but no details were available yet.
A wedding hall and a residential building were also struck.
War crimes
In Geneva, the United Nations human rights office said there was growing evidence of Russian war crimes in Ukraine, including indiscriminate shelling and summary executions.
It said Ukraine also appeared to have used weapons with indiscriminate effects.
Russia denies targeting civilians and says, without evidence, that signs of atrocities committed by its soldiers were faked.
Ukraine has previously said it will punish any soldiers found to have committed war crimes.
The government did not respond immediately to the UN human rights office remarks.
Russia said yesterday it had won the war's biggest fight - the battle for Mariupol, the main port of the Donbas, after an early two-month siege.
President Vladimir Putin said the army would not try to root out thousands of Ukrainian troops still holed up in a huge steelworks there but would barricade them inside.
Today, Russia's defence ministry said they remained "securely blockaded".
Washington dismissed Russia's announcement.
"We still assess that Mariupol is contested, that it hasn't been taken by the Russians and that there's still an active Ukrainian resistance," Pentagon press secretary John Kirby told CNN.
In a Russian-held section of the city, the guns had largely fallen silent and dazed-looking residents ventured out into streets yesterday to a background of charred apartment blocks and wrecked cars. Some carried suitcases.
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Volunteers in white hazmat suits and masks roved the ruins, collecting bodies from inside apartments and loading them on to a truck marked with the letter 'Z', symbol of Russia's invasion.
Maxar, a commercial satellite company, said images from space showed freshly dug mass graves on the city's outskirts.
Ukraine estimates tens of thousands of civilians have died in the city during Russia's bombardment and siege, and says 100,000 civilians are still there and need full evacuation.
Relatives of Mariupol residents feared the worst. Sofia Telehina said her grandmother had cried constantly when they last spoke by phone and said everything was bombed to pieces. "Since then I've not been able to reach her."
