Russia said Monday that its military aims in Ukraine have expanded beyond the industrial Donbas region as its forces launched deadly barrages over the east and the south of the country.
The warning came as the European Commission called on EU countries to slash demand for natural gas to relieve dependence on Russian energy and sidestep Moscow's energy "blackmail".
Russia's foreign minister Sergei Lavrov said in an interview that Moscow's military was no long "only" focused on wresting control of the east Ukraine regions of Lugansk and Donetsk, which have been partially controlled by pro-Moscow rebels for years.
"The geography is different now. It is not only about the DNR and LNR, but also the Kherson region, the Zaporizhzhia region and a number of other territories" he explained to state media.
Russian forces, since invading on February 24, have steadily advanced into each of those regions and sewn destruction as they captured key cities and met fierce Ukrainian resistance.
The steady progress in the east came after Moscow's forces failed early in the invasion to capture the capital Kyiv and were pushed back from Ukraine's second city Kharkiv.
But Russian artillery outside the eastern urban hub has nonetheless pursued an almost constant shelling campaign, and strikes on Kharkiv Wednesday left three dead, local authorities said.
- Western arms a 'direct threat' to Russia -
"There was a 13-year-old boy among them," the regional governor Oleg Synegubov said in a statement on social media.
AFP journalists on the scene saw a man in shock kneeling over the body, covered by a blue sweatshirt and surrounded by shards of broken glass.
In the southern city of Nikopol, meanwhile, Russian shelling on a residential neighbourhood left two people dead, authorities announced.
While the brunt of fighting in Ukraine in recent months has focused on Donbas, a Ukrainian counter offensive in the south has slowly clawed back some Russian-held territory.
Ukraine and military analysts credit Western-supplied long-range artillery with shifting battle field dynamics there and Russian officials have taken note.
Lavrov said Wednesday that Western arms deliveries to Ukraine had played into Moscow's decision to focus beyond the east and said its ambitions could expand even more if the shipments continue.
"We cannot allow the part of Ukraine that (President Volodymyr) Zelensky will control or whoever replaces him to have weapons that will pose a direct threat to our territory and the territory of those republics that have declared their independence," Lavrov said, referring to Donetsk and Lugansk.
- Emergency energy plans -
Mykolaiv, the largest city under Ukraine control near Russian-occupied Kherson and the southern front has been shelled persistently since the beginning of the invasion.
The regional governor on Wednesday announced the city would be closed "for a day or two" in several weeks to process information on people believed to have been collaborating with Russian troops.
A day earlier, governor Vitaliy Kim promised a $100 reward for anyone who could help to identify people who have been collaborating with Russia by providing it with the locations of Ukrainian troops or coordinates of potential targets.
The announcement comes after Zelensky in Kyiv fired several senior law enforcement officials -- including the head of the security services -- accusing their departments of failing to crack down on spies and Kremlin-sympathisers.
The West has responded to Russia's invasion with several packages of damaging sanctions, which in turn has seen Russia cut natural gas supplies to the bloc, spurring a supply and cost crisis.
Announcing an emergency plan Wednesday, the European Commission asked EU countries to reduce demand by 15 percent to secure sufficient storage ahead of winter.
EU commissioners also asked member states to give Brussels special powers to impose compulsory energy rationing if Russia cuts off Europe's gas lifeline.