Burundi's ruling CNDD-FDD party says it is "shocked" that Belgium has advised its nationals to leave the country.
Now was not the time "to sneak off" given the historic atrocities committed by the former colonial power against Burundians, it said in a statement.
Belgium last week said those "whose presence is not essential" should leave because of increasing insecurity.
The unrest began in April when President Pierre Nkurunziza announced he would seek a third term.
Burundi has accused Belgium of links to opposition groups it blames for a spate of killings, charges Belgium denies.
"The Belgians did not only sow divisions in the hearts of Burundians... but on top of that they would whip Burundians in front of their families," the ruling party added, in a statement highly critical of Belgium's colonial role.
Belgium said it had about 500 citizens in Burundi but Robert Misigaro, from the BBC's Great Lakes Service, says there have been no signs of mass evacuations at the airport.
At least 240 people have been killed in unrest since April.
The violence has increased in recent weeks, with bodies found on the streets on a daily basis.
Last week, the UN Security Council unanimously adopted a resolution strongly condemning the escalating violence.
The French-drafted resolution also paves the way for a possible deployment of blue-helmeted UN peacekeepers.
Burundi's constitutional court backed Mr Nkurunziza's third-term bid, as his first term as president did not count towards the constitutional two-term limit because he was chosen by MPs, rather than in a popular election.
Mr Nkurunziza was duly re-elected with 70% of the vote in July.
Correction 20 November 2015: An earlier version of this story wrongly said the CNDD-FDD had urged all Belgians leave the country. This was due to a translation error.