Due to the explosion, the building's entrance was filled with broken glass from the vehicles parked at Pisagua Street. The headquarters' facade was also stained with red paint. So far, there are no casualties reported.
Police arrested six suspects carrying explosives in the headquarters' neighborhood. The detainees spent the night in the Special Anti-Crime Force (FELCC) cells.
"This is a racist and violent act. We ask human rights organizations to pay attention to the attacks and threats suffered by social movements," the Movement Towards Socialism (MAS) presidential candidate Luis Arce tweeted.
"Police arrest six people suspected of Molotov cocktail bombing at COB headquarters."
The attacked building is also the headquarters of the Bartolina Sisa Confederation of Rural and Indigenous Women.
The attack occurred hours after COB leaders called "treason and political maneuvering" the approval of a law that sets October 18 as the deadline for the presidential elections.
"This law was never agreed upon with the Bolivian people. The coup-born regime led by Jeanine Añez has betrayed us," COB leader Juan Carlos Huarachi said, adding that social organizations demand the elections be held on October 11.