Two people were killed in fighting in the capital of Central African Republic and six peacekeepers from Burundi and Cameroon were wounded in an ambush, a spokeswoman for the United Nations mission in the country (MINUSCA) said on Saturday.
Samba-Panza said she would not step down in the face of heightened political pressure and there were signs late on Saturday that tensions could be easing as one militia group withdrew its call for her resignation.
"I will not resign. I must lead this country until the end of my mission," Samba-Panza told state radio.
The unrest is a struggle for power and resources in an impoverished country with reserves of gold and diamonds. Rival communities have also clashed across religious lines.
Those killed overnight include a gendarme and a local leader for a militia known as "anti-balaka", whose adherents follow Christianity and animism.
The peacekeepers were attacked in a neighbourhood near the Bangui airport and two were seriously hurt, Myriam Dessables, a spokeswoman for the country's UN mission MINUSCA, told Reuters.
The United Nations took over peacekeeping in mid-September from a mission run by the African Union. The country was plunged into chaos as mostly Muslim rebels from a coalition called the "Seleka" seized power in March 2013.