The record fine imposed on BP over the 2010 rig explosion and oil spill is a small price to pay for the worst ecological disaster in US history, victims and environmental groups say.

BP agreed Thursday to pay $4.5 billion in US fines for the Gulf of Mexico oil spill and pleaded guilty to 14 counts, including felony manslaughter, in the deaths of 11 workers in the offshore rig blast that caused the disaster.

Stephen Stone, who was working aboard the BP-leased Deepwater Horizon when the explosion tore through the rig on April 20, 2010, welcomed the settlement but said the blame extends to Transocean, which was operating the rig for BP.