Secretary of State John Kerry is traveling to Brussels on Friday to discuss the deadly attacks with top Belgian and European officials.

State Department spokesman John Kirby says Kerry will visit the Belgian capital to "formally express the condolences of the United States for the loss of life" in Tuesday's bombings at the Brussels airport and subway.

He also will voice support for Belgian efforts to investigate the attacks and combat violent extremism.

At least 34 people were killed, including three suicide bombers, and more than 270 were wounded in the attacks claimed by Islamic State extremists.

Kerry is currently in Moscow for talks with President Vladimir Putin and other officials on Syria and Ukraine.