Three people were killed and 11 others injured on June 17 when an explosive device rocked a mall in the tourist district of Colombia's capital Bogota.
Among those killed was a 23-year-old French national who was in the country to do social work at a school, officials said.
The blast, which came from a second-floor bathroom, was called a "cowardly terrorist act" by Bogota's Mayor Enrique Peñalosa.
On Saturday, four men and four women were arrested after authorities served several search warrants in Bogota and the nearby town of El Espinal. The suspects are being held in suspicion of conspiracy, terrorism, homicide, kidnapping and aggravated robbery, Colombia's National Police said.
When asked by reporters, Colombia National Police Chief Jorge Hernando Nieto refused to answer whether those arrested were present at the mall. He said the investigation is ongoing.
President Juan Manuel Santos thanked police, the attorney's general office and the community to collaborate in bringing justice after the attack.
Violence in Colombia
Saturday's arrests have led authorities to solve 14 other smaller attacks with no fatalities reported since 2015, the Colombian attorney general's office said.
"The evidence indicates that the four men and four women are members of the Movimiento Revolucionario del Pueblo ( the People's Revolutionary Movement), a group that has claimed responsibility for many of the attacks," police said in a statement.
MRP, an anti-government militia, is believed to have been created in 2015. Since then, they have pronounced themselves against President Juan Manuel Santos and the ideals of former President and current senator Alvaro Uribe Velez.
The group was linked to a series of simultaneous explosions last year that targeted the offices of health care insurers in Bogota. Authorities said they found flyers signed by the group, CNN affiliate Cable Noticias reported.
Last week, MRP released a statement on social media addressing the June 17 attack.
"We profoundly condemn that criminal act against innocent people and we reject being linked to an act of barbarism, oblivious to our ideas and actions," the group said.
The MRP is not considered as prominent as major terrorist organizations in Colombia, The Revolutionary Armed Forces of Colombia (FARC) and the National Liberation Army (ELN).
In 2015, terrorist activity in Colombia decreased due to the Colombian government's ongoing peace talks and cease fire with FARC and exploratory talks with ELN, according to a report by the US Department of State.