The Obama administration moved Wednesday to punish companies from Belarus and Iran for allegedly providing Syria with weapons and communications gear used to battle rebels in the country’s 18-month-old civil war.

Treasury Department officials also announced sanctions against a Syrian army supply group and a Syrian scientist suspected of overseeing the production of some of the country’s chemical weapons.

The sanctions and other measures are the latest in a series of steps intended to squeeze Syria’s economy and discourage foreign governments from aiding Syria’s armed forces and its beleaguered president, Bashar al-Assad.

The actions “seek to disrupt the flow of weapons and communications equipment to the Syrian regime and help prevent their use against the Syrian people,” said David S. Cohen, Treasury’s undersecretary for terrorism and financial intelligence.

Documents released by the Treasury Department identified a state-owned Belarusan company, Belvneshpromservice, as having attempted to supply fuses for aerial bombs to the Syrian army. Aerial bombs were used by Syrian loyalists as recently as July in attacks against rebel strongholds in Aleppo, the country’s largest city.

The Syrian agency that negotiated the purchase of bomb fuses, the Syrian Army Supply Bureau, also was targeted for sanctions in connection with efforts to procure a wide range of weapons and communications equipment for use against anti-government rebels, including electronic jamming devices, department officials said.

Much of the equipment was flown into the country by Iranian planes owned by the carriers Iran Air, Mahan Air and Yas Air, administration officials said. Treasury documents identified 117 specific aircraft used by the three companies in carrying out routine smuggling operations, often posing as humanitarian relief flights.

Under a law passed by Congress in April, the Treasury Department is authorized to blacklist U.S. or foreign firms that conduct business with any of the sanctioned companies, department officials noted.

The Syrian scientist named in the documents was Amr Armanazi, director of a civilian research agency known as the Scientific Studies Research Center. The center has been linked to Syria’s weapons of mass destruction programs, including biological and chemical weapons research, Treasury officials said in a statement.

During his tenure, Armanazi “oversaw a facility that was involved in the production of sarin nerve agent,” the statement said.