BP said it has reached an $18.7 billion settlement of damages claims from the US government and five states after the 2010 Gulf of Mexico spill.

The US Justice Department said it could be the largest settlement with a single entity in American history and the total value would top $20 billion.

The April 20, 2010 rig explosion and spill killed 11 workers and spewed oil for nearly three months on to the shorelines of several states.

BP said the agreement covered claims from the states Of Alabama, Florida, Louisiana, Mississippi and Texas and 400 local government entities.

BP's London-listed shares extended gains to as much as 5.3 percent.

BP faces a maximum fine of $13.7 billion under the Clean Water Act for its Gulf of Mexico oil spill, after a judge ruled that it was smaller than the U.S. government claimed.

Florida's Attorney General said her state's economic damages lawsuit would continue against Halliburton Co. and Transocean Ltd.