At least six people were killed and dozens wounded on Saturday in the third straight day of riots pitting local residents against police in the Guinean capital Conakry.

Deadly violence has erupted in recent weeks in the west African nation, where opposition activists have accused President Alpha Conde of seeking to rig elections planned for June 30.

At least two people were shot dead Friday in Conakry during fresh clashes between Guinean police and opposition protestors, a hospital source and an opposition official said.

"Three of our supporters were shot dead Friday in Conakry," senior opposition official Cellou Dalein Diallo told AFP. A medic at a hospital in Conakry was able to confirm two deaths.

U.N. Secretary-General Ban Ki-moon called on Friday for calm in the West African nation of Guinea, where political violence has left about 130 people wounded.

"The Secretary-General is concerned about reports of ongoing violent clashes in Guinea, which started in Conakry on Thursday," said a statement released by a U.N. spokesman.