* Toll has reached at least eight dead, 220 injured
* Opposition claims May elections to be rigged
CONAKRY, March 5 (Reuters) - Two more people were killed in clashes between government and opposition supporters in Guinea, officials said on Tuesday, as election protests fuelled by ethnic rivalries spread to more towns in the West African country's interior.
The toll from the protests has reached at least eight dead and some 220 injured since the opposition took to the streets on Wednesday saying the government was attempting to steal legislative elections scheduled for mid May.
Guinea is the world's top supplier of the aluminium ore bauxite and holds rich deposits of iron ore but political turmoil has cooled the investment climate, particularly in the wake of a 2008 military coup.
On Monday, Reuters reported that Guinea's main human rights watchdog, OGDH, said that one protester had been shot dead and six others wounded when security forces opened fire in the crumbling coastal capital.
On Tuesday, OGDH President Thierno Maadjou Sow said another victim killed by a gunshot had been discovered. Officials said a third body had been found but provided no details.
"There are three dead between yesterday and today," government spokesman Damatang Albert Camara said. "We are investigating the circumstances."
Witnesses in Conakry accuse security forces of carrying out reprisals against opposition supporters. Police spokesman Mamadou Alpha Barry said some officers may have made errors.
"There are clashes between supporters of the government and the opposition. That is what we are trying to stop," Barry told Reuters. "At the same time, we are taking steps to stop some members of the security forces who may have committed mistakes."
Guinea's notoriously ill-disciplined security forces have a history of brutal crackdowns on protests.
Gunfire broke out on Monday shortly after Guinea's main opposition leaders boycotted a meeting called by President Alpha Conde to discuss preparations for May's vote, meant to complete a transition to civilian rule after the 2008 coup.
Disturbances have since spread from the capital to other towns in the interior of Guinea. Opposition supporters have clashed with security forces in the opposition fiefdom of Labe, as well as Pita and Mamou.
Behind Guinea's political feuding there is a deep-rooted rivalry between the Malinke and the Peul, its two largest ethnic groups. The Malinke broadly support Conde, who comes from that ethnic group, while the opposition draws heavily from the Peul.
Preparations for the vote, which is essential to unlock hundreds of millions of dollars in European aid to the world's largest bauxite supplier, are being hampered by opposition claims that the government is seeking to rig the outcome. (Reporting by Saliou Samb; Writing by Daniel Flynn; Editing by David Lewis and Michael Roddy)