The US State Department said Wednesday that Russia used "the chemical weapon chloropicrin" against Ukrainian forces.

"As always, such accusations sound completely baseless and unsubstantiated," Kremlin spokesman Dmitry Peskov told reporters when asked about the claims.

The US said that Moscow had violated the Chemical Weapons Convention (CWC).

Chloropicrin is an oily substance known as a choking agent that was widely used during World War I as a form of tear gas.

The US Centers for Disease Control and Prevention label it a "lung damaging agent" that can cause severe irritation to skin, eyes and respiratory systems.

Its use is specifically prohibited by the Organisation for the Prohibition of Chemical Weapons, the implementing body for the CWC.

"The use of such chemicals is not an isolated incident and is probably driven by Russian forces' desire to dislodge Ukrainian forces from fortified positions and achieve tactical gains on the battlefield," the State Department said on Wednesday.

Moscow has signed and ratified the CWC, which outlaws the production and use of chemical weapons.

"Russia has been and remains committed to its obligations under international law," Peskov said on Thursday.

- 'Hostile' -

Moscow said a fresh round of US sanctions -- including on entities in China and other countries where the West has accused firms of helping Russia's military offensive -- would not prevent it forging closer ties with its allies outside of the West.

"The United States is continuing with its overt pressure on these countries. Companies, firms are suffering, but it is not capable of disrupting the development of our bilateral relations with these countries," Peskov said Thursday.

The sanctions, imposed by the US Treasury, targeted companies and individuals that the US said were helping Russia procure key components and parts for its defence sector.

Visiting China last week, US Secretary of State Antony Blinken said he had raised concerns over Beijing's support for Moscow.

"Russia would struggle to sustain its assault on Ukraine without China's support," Blinken told reporters.

Moscow has boosted energy exports to China since losing access to European markets and its imports of equipment, machinery and consumer goods from China have also jumped.

But several Chinese banks have stopped servicing Russian clients after being warned they could be hit with Western sanctions, Russian media outlets have reported in recent months.

Peskov said Thursday Russia would "carry on cooperating in such a way as to gradually minimise the risks from these unfriendly, or rather hostile, manifestations."