WASHINGTON—The U.S. Treasury Department levied a fresh set of sanctions against Russia on Wednesday, blacklisting 15 intelligence agents it says were linked to attacks including the attempted nerve-agent assassination of a former spy in the U.K. and election interference in the U.S. and elsewhere.

The action—against an alleged former intelligence official, the Russian social-media troll farm Internet Research Agency, and others—is part of a broader effort by the Trump administration to punish Moscow for what many officials and analysts see as increasingly aggressive foreign interventions by Russia.

Lawmakers from both parties have pushed the administration to take a tougher stance against Russia, as the special prosecutor’s investigation into the Trump campaign’s ties to the Kremlin has gathered pace in recent weeks.

“The United States will continue to work with international allies and partners to take collective action to deter and defend against sustained malign activity by Russia, its proxies, and intelligence agencies,” Treasury Secretary Steven Mnuchin said.

In a related action, the Treasury Department said it will remove EN+ Group—the Russian energy holding company that owns one of the world’s largest aluminum producers, Rusal—and two subsidiaries from its sanctions list. The administration had been signalingthe action for months, awarding a successful bid by shareholders to force Oleg Deripaska, an ally of Russian President Vladimir Putin and who was blacklisted earlier this year by the U.S., to divest his majority stake in the company.