A retired Burundian army colonel was shot dead in Bujumbura on Wednesday, police said, victim of escalating violence between President Pierre Nkurunziza's security forces and opponents who say his re-election for a third term in July was illegal.

A new round of peace talks was launched in the Tanzanian city of Arusha at the weekend, after previous discussions in Burundi and Uganda over the past year collapsed or stalled.

READ: Burundi opposition group says ready for any new peace talks

ALSO READ: Burundi government to attend peace talks in Tanzania

Police said the former officer, named as Rufyiri Lucien, was shot as he sat in his car waiting for his gate to be opened in the Ngagara neighbourhood.

"The victim was shot in the head while his son, who was opening for him, was slightly injured," Moise Nkurunziza, deputy spokesman for the police, told Reuters.

Local residents said the attackers were driven to the location in a pick-up truck and were dressed in police-like uniforms.

More than 450 people have been killed in Burundi since April 2015 when President Nkurunziza announced he was standing for a third term. Opponents said his move violated the constitution and a deal that ended a civil war in 2005, but Nkurunziza argued that he had judicial support for his additional term.