Russian and Belarusian athletes who were accepted via open registration to the Boston Marathon and reside in their home countries will not be allowed to compete in this month's event, the Boston Athletic Association (BAA) said on Wednesday.
Runners who are Russian and Belarusian citizens but reside outside either country will be permitted to compete but not under the Russian or Belarusian flag.
The restrictions, which also apply to the 5K race, are the latest in a series of sanctions across global sport in response to Russia's invasion of Ukraine.
Belarus, a key staging area for the invasion, has faced broad punishments as well.
"We are horrified and outraged by what we have seen and learned from the reporting in Ukraine," BAA President and CEO Tom Grilk said in a statement.
"We believe that running is a global sport and, as such, we must do what we can to show our support to the people of Ukraine."
The BAA said it will not recognize country affiliation or the flag of Russia or Belarus at any of its races and events "until further notice."
The annual road race is the world's oldest marathon and one of six that comprise the prestigious World Marathon Majors, attracting some of the world's top runners.
This year's race is set for April 18.
Reporting by Amy Tennery in New York; Editing by Ken Ferris