Elliott Investment Management is seeking seats on the board of oil refiner Phillips 66, the latest effort in a multi-year campaign pushing the company to sell assets, improve operational performance and bolster board oversight.

With a more-than-$2.5 billion stake in Phillips 66, Elliott has pushed for a streamlining of the oil refiner and seeks more representation on the company’s board.

Phillips 66 (NYSE:PSX) +1.6% in early trading Wednesday as activist investor Elliott Management, which has built a $2.5B-plus stake in the refiner, discloses it will seek seats on the company's board.

Activist investor Elliott Management has built a near 5% stake in BP and is pushing the oil company to take radical action to transform its performance, including a big divestment programme, a source familiar with the matter told Reuters on Thursday.

Elliott Investment Management is demanding BP Plc make drastic cost cuts and divestments to strengthen its future as a standalone company, people with knowledge of the matter said.