By David Shepardson

WASHINGTON (Reuters) -The Biden administration on Wednesday added 24 companies and other entities to an export control list for supporting Russia’s military or defense industrial base, Pakistan's nuclear activities or for supplying an Iranian electronics company.

The entities, based in Latvia, Pakistan, Russia, Singapore and Switzerland, were added over U.S. national security and foreign policy concerns, the Commerce Department said.

The companies include Fiber Optic Solutions in Latvia, which produces fiber optic gyroscopes and other equipment and Russia's AO Kraftway Corporation PSC, which calls itself one of the biggest Russian IT companies. The company says it builds and sells a wide range of IT solutions including hardware manufacturing.

Also on the list are Russian AO Scientific Research Center for Electronic Computing, LLC Fibersense, and Scientific Production Company Optolin, AO PKK Milandr; Milandr EK OOO; Milandr ICC JSC; Milur IS, OOO; (OOO) Microelectronic Production Complex (MPK) Milandr; and Ruselectronics JSC and Swiss based Milur SA.

The Commerce Department also added four trading and supply companies in Singapore for supplying or attempting to supply an Iranian electronics company, Pardazan System Namad Arman

(PASNA), that was sanctioned by the U.S. Treasury in 2018.

The Biden administration also added 10 companies in Pakistan and UAE that it says pose unacceptable risks of using or diverting items for Pakistan's unsafeguarded nuclear activities or are involved Pakistan's "nuclear activities and missile proliferation-related activities."

None of the companies was immediately available for comment.

The United States has made muscular use of export controls and the entity list to punish companies over their support of the Russian military and to curb the flow of foreign technology to Russia since Moscow invaded Ukraine in February.

Suppliers of U.S. goods must seek a special a difficult-to-obtain license before shipping to companies added to the list.

(Reporting by David Shepardson and Karen Freifeld; Editing by Nick Macfie)