KYIV/MARIUPOL (REUTERS, AFP) - Ukrainian President Volodymyr Zelensky warned that Russia's invasion of his country was just the beginning and that Moscow has designs on capturing other countries after a Russian general said it wants full control over southern Ukraine.

"All the nations that, like us, believe in the victory of life over death must fight with us. They must help us, because we are the first in line. And who will come next?" Mr Zelensky said in a video address late on Friday (April 22).

Mr 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 Transnistria, a breakaway Russian-occupied part of Moldova in the west.

That would cut off Ukraine's entire coastline and mean Russian forces pushing hundreds of miles west beyond current lines, past the major Ukrainian coastal cities of Mykolaiv and Odessa.

The statement was one of the most detailed about Moscow’s ambitions in Ukraine and suggests Russia does not plan to wind down its offensive there anytime soon.

On Twitter, Ukraine's Defence Ministry said Major General Minnekayev's statement showed Russia was no longer hiding its intentions.

Moscow, it said, had now "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".

On Saturday, a Russian strike killed at least five people, including a baby, and wounded 18 others in Ukraine’s Black Sea city of Odessa, Kyiv said, warning the toll would likely rise.

“Five Ukrainians killed and 18 wounded. And those are only the ones that we were able to find. It is likely that the death toll will be heavy,” the head of Ukraine’s presidential office Andriy Yermak said on Telegram. “A three-month-old baby was among those killed.”

Earlier on Saturday, Ukraine’s Foreign Minister Dmytro Kuleba said: “The only aim of Russian missile strikes on Odessa is terror.” Ukraine’s air force said its defence systems intercepted two Russian TU-95 missiles that it said were fired from the Caspian Sea.

But it said four other missiles hit the city, including civilian infrastructure. “Unfortunately, two missiles hit a military facility and two hit residential buildings,” the air force’s southern command said on Facebook.

Meanwhile, President Zelensky has spoken with British Prime Minister Boris Johnson about a “new phase” of military aid, including the provision of heavy weapons, the president’s deputy chief of staff Andriy Sybiga said on Saturday.

Speaking on national television, Sybiga said the pair also talked about further financial support for Ukraine on the call.

Russia says it is conducting a "special military operation" to demilitarise Ukraine and liberate its population from dangerous nationalists. Ukraine and its Western allies call Russia's invasion an unjustified war of aggression.

Major General Minnekayev said Russian speakers were oppressed in Transnistria, something Moldova and Western leaders reject.

Moldova's Foreign Ministry said it had summoned Moscow's ambassador on Friday to express "deep concern" about the general's comments. Moldova was neutral, it said.

Moldova last month formally applied to join the European Union, charting a pro-Western course hastened by Russia's invasion. Its president Maia Sandu said on Twitter that on Friday Moldova had submitted its first questionnaire for European Union membership as it sought "a better, safer & more prosperous future."

United States State Department spokesman Jalina Porter declined specific comment on Mr Minnekayev's statement but said Washington firmly supported Moldova's sovereignty and was "clear-eyed" about events on the ground.

"No one should be fooled by the Kremlin's announcements," Ms Porter said.

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.

As US Secretary of State Antony Blinken met with Ukrainian Prime Minister Denys Shmyhal in Washington, Mr Zelensky said allies were finally delivering the weapons Kyiv had asked for.

US President Joe Biden said on Thursday he had authorised a further US$800 million (S$1.1 billion) in military aid for Ukraine, including heavy artillery, ammunition and tactical drones.

Canada said on Friday it had provided more heavy artillery to Ukraine, following up on a pledge earlier this week.

A senior EU official said the next couple of weeks would likely be decisive.

"This is not a fairy tale with an imminent happy ending," he told reporters. "We are likely to see a very significant increase in the intensity of Russian military attacks in the east (and) the coast."

Ukraine's military said Russian forces had increased attacks along the front line in the east and were attempting an offensive in the Kharkiv region, north of their main target, the Donbas.

Ukrainian military commands in the south and east said they had repelled 11 Russian attacks, killing up to 130 soldiers while destroying 12 tanks and 27 other armoured vehicles, details Reuters could not independently confirm.

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 on Friday.

War crimes

In Geneva, the United Nations human rights office said there was growing evidence of Russian war crimes, 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.

Russia's Defence Ministry said thousands of Ukrainian troops holed up in a huge steel works in Mariupol, the main port of the Donbas, were "securely blockaded", a day after President Vladimir Putin said the army would not bother rooting them out.

Mr Putin has declared victory in the city after a nearly two-month siege. In a Russian-held section of Mariupol, the guns had largely fallen silent and dazed-looking residents ventured out this week to a background of charred apartment blocks and wrecked cars.

Volunteers in white hazmat suits and masks roved the ruins, collecting bodies from apartments and loading them on to a truck marked with the letter "Z", symbol of Russia's invasion.

Ukraine estimates tens of thousands of civilians have died in Russia's siege of the city and says 100,000 civilians are still there and need full evacuation.

Ukrainian Deputy Prime Minister Iryna Vereshchuk on Friday said "there is a possibility" a humanitarian corridor out of Mariupol could be opened up on Saturday.

In Lviv, Sofia Telehina said her grandmother in Mariupol 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," she said.

UN Secretary-General Antonio Guterres will visit Moscow on Tuesday to meet Mr Putin and discuss urgently bringing peace to Ukraine, a spokesperson said, adding that Mr Guterres will then head to Kyiv for talks with Mt Zelensky.

The Pentagon said more than 20 countries would attend US-hosted defence talks in Germany next week to consider Ukraine's long-term defence relationships once the war is over.