Local administrations and witnesses said that at least four people were killed on Sunday during separate incidents of violence in Burundi's capital Bujumbura.
Bujumbura Mayor Freddy Mbonimpa, a member of President Pierre Nkurunziza's CNDD-FDD party, said his home was damaged when 10 people attacked the house in Rohero neighbourhood, which has seen little violence so far.
"Around 10 assailants ... shot and threw grenades at my house. We fortunately registered no death because my guard responded," Mbonimpa told Reuters.
Violence spread in Burundi since April when the country's current President Pierre Nkurunziza decided to run for a controversial third term which led to mass protests and violence throughout the country.
Dozens have been killed in protests and hundreds of thousands of people have fled the country.
Nkurunziza won the elections in July.
A police post was attacked in the southern region of the capital causing the death of one police officer while another was injured according to security sources who spoke on the condition of anonymity.
Another three people were killed in the Mukaza district of the capital according to Dieudonné Nduwayo, administrative secretary of Bujumbura's Bwiza zone.
Another police officer who asked for anonymity said shootings started at around 9.00 pm local time in areas like Mutakura.
At midnight the gunfire was intensified and was heard across Bujumbura and lasted for hours.
The United Nations Security Council asked last week the Secretary-General Ban Ki-moon to make a plans within 15 days to increase the UN presence in Burundi.
Concerns arise about expected violence that could turn into an ethnic conflict in Burundi similar to that which happened in neighbouring Rwanda in the 1994 genocide.