The slain workers had gone to carry out some repair works on a damaged portion of the the Nigerian National Petroleum Corporation (NNPC) pipeline when they were shot at by some gunmen who were siphoning oil from ruptured areas.
Spokesman for the NNPC Fidel Pepple said fire erupted as a result of the gun shots but was promptly put off by a team of technicians and engineers who cut off petroleum supply to the pipelines.
"The vandals laid ambush for them and opened fire from a distance, killing three staff members and injuring scores," he said.
Petroleum pipelines are ruptured frequently in Nigeria by oil thieves who siphon the products to sell at black markets.
In June 2009, a pipeline eruption in Ilado suburb of Lagos killed scores of persons who were scooping fuel.