Burundi's government has promised to crack down on a wave of protests, accusing opposition groups of providing cover for a "terrorist enterprise".
The security minister also said that an attack on Friday which killed three people, including two police officers, was linked to the demonstrators.
Meanwhile, protesters have called for a two-day halt in their campaign against President Nkurunziza's re-election bid.
It is the biggest unrest Burundi has seen since a civil war ended in 2005.
The deadly attack late on Friday was carried out in the capital Bujumbura by unidentified gunmen using automatic weapons and grenades.
On Saturday Security Minister Gen Gabriel Nizigama linked the incident to six days of protests by opposition and civil society groups.
"These demonstrations provide cover for a terrorist enterprise," he said.
Security forces, he added "will do everything to stop this uprising". From now on, he said, the demonstrators would be regarded as "criminals, terrorists and even enemies of the country".
Also on Saturday, protest organisers announced a pause in their campaign against President Pierre Nkurunziza's decision to run for a third term in elections in June.
"We decided to stop demonstrations for two days, first to allow those who lost their family members in the protests to observe mourning and, second, we want the protesters to regain energy before resuming the fight Monday," said civil society leader Pacifique Nininahazwe.
At least seven people have died in the protests, which have seen violent clashes.
Under Burundi's constitution, presidents can only be elected to two terms in office, but Mr Nkurunziza's allies say his first term does not count as he was appointed by parliament.
Mr Nkurunziza has been in power since 2005, when a 12-year civil war officially ended.
More than 300,000 people died in the conflict between the minority Tutsi-dominated army and mainly Hutu rebel groups, such as Mr Nkurunziza's CNDD-FDD.