The United Nations cited "credible accusations" Wednesday that Moscow's forces have forcibly taken Ukrainian children to Russia, while Russian President Vladimir Putin accused the West of benefitting from the eased grain blockade.

Kyiv meanwhile said its forces had recaptured significant territory in a counter-offensive southeast of Kharkiv that experts say could threaten key Russian supply routes.

As Europe girded for the prospect of winter with diminished energy supplies, the European Commission proposed a series of measures to control energy skyrocketing prices and punish Moscow for invading Ukraine, including a price cap on Russian gas.

"We are facing an extraordinary situation, because Russia is an unreliable supplier and is manipulating our energy markets," warned EU chief Ursula von der Leyen.

"Our unity and our solidarity will ensure that we will prevail," she added.

In Washington and at a UN Security Council meeting, Moscow was accused of forcing large numbers of Ukrainian non-combatants into detention camps and even prisons via a Kremlin-directed "filtration" program, and removing children from the war zone to hand over to adoptive parents inside Russia.

"We are concerned that the Russian authorities have adopted a simplified procedure to grant Russian citizenship to children without parental care, and that these children would be eligible for adoption by Russian families," Ilze Brands Kehris, the assistant UN secretary-general for human rights, told the Security Council.

She said Russian forces are putting Ukrainians in occupied territories through invasive security checks that have involved numerous human rights violations.

Some Ukrainians judged as close to the Ukraine government or military have been tortured and forcibly removed and sent to Russian penal colonies and other detention centers, she said.

The US State Department said Russian President Vladimir Putin's office is directly managing the relocation of Ukrainians into Russia, and doing it as part of a plan to annex occupied territory.

"Russia has systematically used the practice of forced deportations previously, and the fear and misery it evokes for people forced to live under the Kremlin's control are hard to overstate," said State Department deputy spokesman Vedant Patel.

But Russian UN Ambassador Vasily Nebenzya called the allegations unfounded and said what was labelled "filtration" was simply registering Ukrainians willingly fleeing the war to Russia.

"As far as we can judge similar procedures are applied in Poland and other countries of the European Union against Ukrainian refugees," he told the Security Council.

Putin accused Europe of taking advantage of Russia's lifting of a blocked on Ukraine grain exports to help itself while poorer countries were being deprived of essential food.

Official data collected by a joint centre in Istanbul monitoring implementation of the recent grain export agreement showed 30 percent of the grain reaching low and lower-middle income countries.

Data compiled as of Wednesday showed Turkey receiving 20 percent of the grain followed by Spain (15 percent) and Egypt (10 percent).

But much of the grain reaching Turkey and some other destinations is then re-sold under agreements not monitored by the Istanbul centre.

"Almost all the grain exported from Ukraine is sent not to the poorest developing countries, but to EU countries," Putin alleged.

European countries were acting as "colonialists," he said, "once again simply deceived developing countries."

"Maybe we should think about limiting the export of grain and other produce along this route?" he said.

A US official dismissed Putin's remarks as untrue, noting that some grain sent to Europe was then processed for poor nations.

Late Wednesday Ukrainian President Volodymyr Zelensky said that Kyiv troops have recaptured several settlements in the Kharkiv region, though he declined to name them.

The US Institute for the Study of War, which follows in detail the fighting, said the Ukraine counterattack was near Balakliya and probably drove Russian forces back to the north side of the Severskyi Donets and Serednya Balakliika rivers.

It appeared Ukraine forces also recaptured Verbivka and that Russian forces may have destroyed bridges to prevent Ukrainian fighters from pursuing them, ISW said.

"Russia's deployment of forces from Kharkiv and eastern Ukraine to Ukraine's south is likely enabling Ukrainian counterattacks of opportunity," it said.