Nigeria is Africa's largest oil producer
Hundreds of villagers have been evacuated by air by the Nigerian arm of the Chevron Texaco oil company from areas affected by unrest in the southern Delta region.
Over the past week at least a dozen people have been killed and hundreds of others injured in a conflict between two local communities, the Ijaw and Itsekiri.
Oil installations have also been targeted and production in the area has been severely disrupted.
Chevron Texaco and Shell, the largest oil producer in Nigeria, are losing more than 150,000 barrels of oil a day, about 8% of Nigeria's total production.
Both companies have also been withdrawing staff from the area to ensure their safety. Nigeria is Africa's largest oil producer.
The government has ordered up to 1,000 troops to the region to end the clashes and the rivers and creeks south of the town of Warri have been declared a no go area.
On Wednesday, President Olusegun Obasanjo issued a strong warning that the current high level of violence in the country was posing a threat to the success of next month's elections.
The BBC's Dan Isaacs in Warri reports that refugees from the crisis are arriving in the town with harrowing stories of the violence.
One woman evacuated by Chevron said that youths from the opposing Ijaw community had attacked her Itsekiri village and shot and killed her son.
The Ijaw are demanding more political representation and compensation from oil companies operating in the area. They say the oil industry has polluted their fishing communities.
A militant Ijaw leader said that protests against the Itsekiri and the oil companies would continue until the government addressed this issue.
Our correspondent says that this is extremely unlikely ahead of the elections and he says it is difficult to see how an effective poll can take place in this part of the southern Delta under the present circumstances.
He adds that even if the unrest subsides, many hundreds, perhaps thousands of people have been displaced and election officials will be extremely wary about operating in such an unstable region.