"When Germany continues buying gas and oil from Russia, it means that they are paying their money to construct new military machines, new bombs, which are killing Ukrainians," Natalia Gozak, head of the EcoAction civil society group, said from Lviv.
Gozak said European politicians need to choose between an embargo's economic "inconveniences" and the deaths of Ukrainians.
In the United States, activists from the Extinction Rebellion group blockaded a New York newspaper printing facility, where they called for more media coverage of climate change.
Youth protesters also gathered in locations including Bangkok and Stockholm, where Swedish activist Greta Thunberg joined the school strike - a weekly protest she began as a solitary student in 2018 to call for urgent action to address climate change.
The protests aim to amplify demands for climate action on Earth Day, when people worldwide celebrate and mobilise in support of protecting the environment. They come three weeks after a U.N. climate scientist report warned there is little time left for reining in greenhouse gas emissions sufficiently to prevent the worst impacts of climate change.