The BBC's correspondent in Colombia, Jeremy McDermott, said that the timing of Colombia's announcement is fortuitous.
The arrests are the first effective response to the grusome Easter massacre of 42 peasants.
The army said on Monday that 57 members of the AUC - the right-wing United Self Defence Forces of Colombia - had been arrested over the past three days. They have killed three more.
"This is the heaviest blow in history against the illegal self-defence forces," said Captain Alberto Rojas Torres, commander of the Navy's Pacific fleet.
Massacre
In the Easter attack, the AUC claimed they had killed leftist guerrillas, but those murdered were unarmed, and according to the authorities some had been killed with chainsaws.
The BBC's correspondent in Colombia, Jeremy McDermott, said that the timing of Colombia's announcement is fortuitous.
The United States supports the Colombian army to the tune of more than $1bn and Europe, which has demanded action against the paramilitaries, is debating how much aid to give Colombia.
Human rights groups have long alleged that the army maintains links to the paramilitaries and turns a blind eye to their violence.
Same enemies
The paramilitaries and the Colombian government share some of the same enemies - the leftist Revolutionary Armed Forces of Colombia (FARC) and the National Liberation Army (ELN).
Last year there were almost 250 massacres, claiming 1,200 lives, and the paramilitaries were responsible for the majority of them.
The violence is spawned by a a deep divide between the right-wing paramilitary groups, often in the pockets of drug traffickers and landowners, and the peasants and human rights workers who they suspect help left-wing guerrillas.
The AUC was included on the US terrorism list because of "a dramatic increase in (AUC) activities and a tendency to change their tactics toward more terrorist tactics, including kidnappings, for example, or murders of civilians," said US State Department counter-terrorism co-ordinator Edmund Hull.
This means that all AUC members are barred entry to the United States and prevented from doing business with US companies or citizens.