Russia threatens broad Ukraine offensive

A missile strike on the northeastern city of Kharkiv on Saturday wounded three civilians, its governor said, though Russia's main attacks appeared focused southeast of there in Luhansk and Donetsk.

Those two provinces, parts of which were held by pro-Russian separatists before the conflict began in February, comprise the eastern industrial region of the Donbas.

Ukrainian officials reported strikes in both on Saturday, while Britain's Ministry of Defence said Moscow was assembling reserve forces from across Russia near Ukraine.

Donetsk regional Governor Pavlo Kyrylenko said on the Telegram messaging service that a Russian missile had struck Druzhkivka, a town behind the front line, and reported shelling of other population centres.

Luhansk Governor Serhiy Gaidai said on Telegram that Russian forces were "firing along the entire front line", though a subsequent Ukrainian counter-attack had forced Moscow to halt its offensive.

Ukraine President Volodymyr Zelenskiy said the Russian army had targeted civilians on purpose.

"It fired precisely at the residential sector - absolutely deliberately, purposefully, at ordinary houses and civilian objects," he said in a statement.

Russia, which claimed control over all of Luhansk province last weekend, denies targeting civilians.

Zelenskiy also dismissed several of Kyiv's senior envoys abroad, saying it was part of "normal diplomatic practice." He said he would appoint new ambassadors to Germany, India, the Czech Republic, Norway and Hungary.

Zelenskiy has urged his diplomats to drum up international support and high-end weapons to slow Russia's advance.

US President Joe Biden signed a weapons package for Ukraine on Friday worth up to $US400 million ($A583 million), including four additional high mobility artillery rocket systems (HIMARS).

But Ukraine suffered a diplomatic setback on Saturday, when Canada said it would return a repaired turbine that Russia's state-controlled Gazprom used to supply natural gas to Germany. Ukraine had argued that a return would violate sanctions on Russia.

On Saturday US Secretary of State Antony Blinken, urging the international community to join forces to condemn Russian aggression, told journalists he had raised concerns with his Chinese counterpart Wang Yi over Beijing's alignment with Moscow.

The pair held over five hours of talks on the sidelines of the G20 gathering of foreign ministers on the Indonesian island of Bali. On Friday, Russia's Sergei Lavrov had walked out of a meeting there, denouncing the West for "frenzied criticism".

The Chinese foreign ministry said, without giving details, that Wang and Blinken had discussed "the Ukraine issue".

It also quoted Wang as saying that Sino-American relations were in danger of being further led "astray", with many people believing that "the United States is suffering from an increasingly serious bout of 'Chinaphobia'."

Shortly before the Russian invasion, Beijing and Moscow announced a "no limits" partnership, although US officials have said they have not seen China evade US-led sanctions on Russia or provide it with military equipment.

Kharkiv's Governor Oleh Synehubov said on Telegram that, as well as the missile strike, fighters had repulsed two Russian attacks near Dementiivka, a town situated between the city and the border with Russia.

Russia's defence ministry said its forces hit two "bases of foreign mercenaries deployed near Kharkiv".

Ministry spokesperson Igor Konashenkov also said troops had destroyed ammunition depots in the Mykolaiv, Dnipropetrovsk and Donetsk regions.

Russian-backed forces in the territory of the self-proclaimed Donetsk People's Republic (DPR) said three people died and 17 were wounded there in the past 24 hours as Ukrainian forces shelled 10 locations.

Alexei Kulemzin, mayor of Donetsk, wrote on Telegram that two women had died as a result of shelling in the city's Kirovskyi district.

Reuters could not independently verify battlefield accounts.

Australian Associated Press