The US government announced Wednesday that it will expand the export restrictions imposed on Russia earlier this month as punishment for the poisoning of opposition leader Alexei Navalny.

The new measures, effective Thursday, prevent export to Russia of more items controlled for national security reasons, including some technology, software and parts, the Commerce Department said.

"The Department of Commerce is committed to preventing Russia from accessing sensitive US technologies that might be diverted to its malign chemical weapons activities," the statement said.

The Commerce Department of did not give details of the goods subject to the expansion of the sanctions, first announced on March 2, when Washington also froze assets in the United States of seven senior Russian officials, including Alexander Bortnikov, head of the Federal Security Service (FSB).

The United States had also blacklisted 14 companies or entities out of fear they could help Russia develop chemical weapons.

Washington blames Moscow for last year's poisoning of Navalny, a charge Russia has denied. 

The opposition leader returned to Russia in January after being treated for the poisoning in Germany, and is serving a two-and-a-half year jail term in a penal colony outside Moscow.