The Kremlin on Thursday rejected allegations by the United States that Russian forces had used a "chemical weapon" in Ukraine.
The US State Department said on Wednesday it had determined that Russia used "the chemical weapon chloropicrin" against Ukrainian forces.
"We have seen the news about this. As always, such accusations sound completely baseless and unsubstantiated," Kremlin spokesman Dmitry Peskov told reporters when asked about the accusations.
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.
Earlier, the US State Department accused Russia Wednesday of having used a chemical weapon against Ukrainian forces in violation of the Chemical Weapons Convention, while also announcing fresh sanctions against Moscow.
In addition to the chemical agent chloropicrin, Russia also used "riot control agents (tear gas) as a method of warfare in Ukraine, also in violation of the CWC," the department said in a factsheet.
"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.
Meanwhile the US Treasury Department announced sweeping sanctions aimed at crippling Russia's military and industrial capabilities -- including targeting nearly 300 entities in Russia, China and other countries accused of supporting President Vladimir Putin's invasion.
The sanctions are meant to punish companies that help Moscow acquire weapons for its war in Ukraine. They also target Russian government entities and companies involved in the country's chemical and biological weapons programs.
Russia has said it no longer possesses a military chemical arsenal, but the country faces pressure for more transparency over the alleged use of toxic weapons.
According to the US National Institutes of Health, the chemical chloropicrin is used both as a warfare agent and pesticide. If inhaled, it poses a health risk.
- 'Sand in the gears' -
"Today's actions will further disrupt and degrade Russia's war efforts by going after its military industrial base and the evasion networks that help supply it," Treasury Secretary Janet Yellen said in a statement.
The accusations and sanctions come a week after US President Joe Biden signed a much-delayed bill to provide new funding for Ukraine as Kyiv's military struggles to hold back Russian advances.
"Even as we're throwing sand in the gears of Russia's war machine, President (Joe) Biden's recently-passed National Security Supplemental is providing badly-needed military, economic, and humanitarian support to bolster Ukraine's courageous resistance," Yellen said.
"Combined, our support for Ukraine and our relentless targeting of Russia's military capacity is giving Ukraine a critical leg-up on the battlefield."
As part of the measures, the State Department blacklisted additional individuals and companies involved in Moscow's energy, mining and metals sectors.
The sanctions also targeted individuals connected to the death of Russian opposition leader Aleksey Navalny who died in a Siberian prison in February.
The almost 300 targets sanctioned included dozens of actors accused of enabling Russia to acquire desperately needed technology and equipment from abroad, the Treasury said.
Some of those targeted were based in countries such as China that have faced increasing pressure from Washington over support for Russia during its 15-month invasion of Ukraine.
"This support enables Russia to continue its war against Ukraine and poses a significant threat to international security," the Treasury Department said.
Other than China, targeted non-Russian entities were located in Azerbaijan, Belgium, Slovakia, Turkey, and the United Arab Emirates.
These companies "enable Russia to acquire desperately-needed technology and equipment from abroad," the statement said.
Missile attack injures 13 in Ukraine's Odesa
A Russian missile attack injured 13 people in Ukraine's southwestern city of Odesa, its mayor said early Thursday, after similar strikes earlier in the week killed at least eight.
"Another Russian ballistics attack on Odesa," the city's mayor Gennadiy Trukhanov said on Telegram.
"A total of 13 people were injured," he said, adding that rescuers were fighting a large-scale fire without providing details.
Oleg Kiper, governor of the Odesa region, said on Telegram early Thursday that a "Russian missile attack on Odessa" had injured 14 people.
"Civilian infrastructure, including postal warehouses, was damaged," he added.
Odesa, a Black Sea port vital for Ukrainian exports, has been regularly targeted by deadly missile and drone attacks.
Local authorities said Wednesday at least three people had died in a Russian missile attack on the city.
Five people were killed on Monday in another Moscow-led attack, authorities said.
Russia has relentlessly hit Ukrainian cities for months and is making a push on the front in eastern Ukraine ahead of the arrival of crucial US weapons.