The United States on Thursday imposed sanctions on a Chinese company for allegedly providing satellite imagery of Ukraine to help Russia's Wagner mercenary group, while American lawmakers pushed for stronger action against Beijing.

The Treasury Department and State Department announced a slew of actions as they formally designated the Wagner Group as a transnational criminal organization, a move previewed last week by the White House.

The new sanctions "will further impede the Kremlin's ability to arm its war-machine that is engaged in a war of aggression against Ukraine, and which has caused unconscionable death and destruction," Secretary of State Antony Blinken said in a statement.

Among the firms targeted was Changsha Tianyi Space Science and Technology Research Institute Co., a Chinese firm which the Treasury Department said has provided satellite imagery over Ukraine to the Wagner Group.

"These images were gathered in order to enable Wagner combat operations in Ukraine," said a statement by the Treasury Department, which also announced sanctions on a Luxembourg-based subsidiary of the Chinese company.

China is officially an ally of Russia but the United States has trumpeted what it sees as Beijing's tepid support for the war in Ukraine including a refusal to supply Moscow with weapons.

But US officials have been concerned about activities by private Chinese companies, which Washington believes are unlikely to be working at the behest of the Chinese government but could be stopped by Beijing.

"We will bring to their attention when we see violations of sanctions by their companies," Victoria Nuland, the State Department's number three official, told a Senate hearing Thursday.

She was responding to senators who called for sanctions against China unless it curbs exports of technology critical to missiles and other military applications by Russia.

"I understand that there has been evidence that Chinese companies including working through Hong Kong have been exporting dual-use technologies including semiconductor chips," said Bob Menendez, the Democratic chairman of the Senate Foreign Relations Committee.

"It seems to me that we should not forsake the potential of sanctions against China if it is providing critical assistance and it shouldn't be able to hide behind some companies," he said.

"We need to cut the head of the snake off in every way we can."

The Treasury Department also imposed sanctions on an aviation firm based in the United Arab Emirates, Kratol, which it said had provided aircraft for the Wagner Group to move personnel and equipment between the Central African Republic, Libya and Mali.

The Wagner Group -- headed by Yevgeny Prigozhin, a businessman close to Russian President Vladimir Putin -- has been especially active in the Central African Republic, where the Treasury Department blacklisted firms seen as part of the Russian unit.

The Wagner Group has taken an increasingly prominent role in Ukraine as it sends to the battlefield Russian inmates who are promised clemency.

The White House said last Friday that Wagner has about 50,000 fighters in Ukraine, 80 percent of them drawn from prisons.