(CNN) -- Six people were killed and 33 were injured in apparent clashes at a displaced persons camp in Sudan's Darfur region on Saturday, days after another attack in the region left 37 dead, officials said.
Three of the injured are in critical condition, said Chris Cycmanick, spokesman for the African Union-United Nations Mission in Darfur.
The violence occurred in at the Hamadiya internally displaced persons camp in Zalingei, in West Darfur state, Cycmanick told CNN. Gunshots rang out sporadically in the camp from midnight Friday to around 8 a.m. Saturday, he said.
"We don't know who was responsible for attack," Cycmanick said. "There was apparently fighting between two groups."
Earlier this week, men on horses and camels slaughtered 37 and left 30 injured at a market elsewhere in Darfur, Cycmanick said.
He added it was unclear who was responsible for that attack, which occurred Thursday afternoon at a market about 40 miles west of El-Fasher, the capital of Sudan's North Darfur state.