The assaults come before a presidential vote on Sunday that will determine whether incumbent President Touadera will stay in power.
Three Burundian peacekeepers have been killed by "unidentified armed combatants" in the Central African Republic, the United Nations said.
The announcement on Friday came after a rebel coalition fighting the government called off a ceasefire ahead of a tense general election due to take place Sunday.
"Three peacekeepers from Burundi were killed and two others were wounded" following attacks on UN troops and Central African national defense and security forces, the UN said in a statement.
The assaults took place in Dekoa, central Kemo Prefecture, and in Bakouma, in the southern Mbomou Prefecture, it said, without providing further details.
Election around the corner
Sunday's elections are deemed a key test of CAR's ability to recover stability.
In the week before voting day, incumbent President Faustin Archange Touadera accused his predecessor Francois Bozize of plotting a coup, a militia briefly seized the country's fourth biggest town, and Russia and Rwanda sent military personnel to help shore up his government.
Sixteen candidates are running for president, including three women and Touadera. There are more than 1,500 candidates for 140 seats in the national assembly. More than 1.86 million voters are registered, but more than 598,000 refugees in neighboring countries will not vote, according to the UN.
The mineral-rich Central African Republic has faced deadly inter-religious and inter-communal fighting since 2013, when predominantly Muslim Seleka rebels seized power from Bozize after long claiming marginalisation.
Resistance to Seleka rule eventually led to Muslims being targeted en masse, with some beaten to death, mosques destroyed and tens of thousands forced from the capital in 2014.
Despite a 2019 peace agreement between the government and 14 rebel groups, intermittent violence and human rights abuses have continued.
The most recent insecurity began after the Constitutional Court rejected the candidacy of Bozize, who returned from exile a year ago.
His candidacy did not satisfy the “good morality” requirement.
Bozize, who took power in a coup in 2003 and ruled until 2013, faces an international arrest warrant for “crimes against humanity and incitement of genocide.” He also faces UN sanctions for his alleged role in supporting the anti-Balaka groups that resisted the Seleka in 2013.