BP said on Friday that its ruptured Gulf of Mexico well that caused the world's worst marine oil spill will be permanently sealed on Saturday.

The oil company's relief well intersected the blown-out Macondo well on Thursday, and on Friday afternoon BP began pumping in cement that will result in the so-called "bottom kill" of the well.

"The pumping procedure is expected to take a few hours," BP spokesman Daren Beaudo said. After the cement cures, the company expects the well to be completely sealed, he said.

Pumping started at 1:30 p.m. CDT (1830 GMT), Beaudo said.

After that, the relief well will be plugged and abandoned, BP said earlier on Friday.

BP sealed off all oil flow with a cap on the wellhead on July 15. Before then, the well spewed more than 4 million barrels of oil into the sea, damaging coastlines along the U.S. Gulf Coast, killing wildlife and hurting the livelihood of fishermen and others.

The well rupture on April 20 triggered an explosion and fire on Transocean Ltd's Deepwater Horizon rig that killed 11 workers and sunk the vessel off the coast of Louisiana. – Reuters