NEW YORK (AP) — ConocoPhillips, the nation's third-largest oil company, said Thursday that it will split itself into two separate publicly traded companies and its CEO and Chairman Jim Mulva plans to retire once the transaction is complete.

Its shares jumped $3.60, or 4.8 percent, to $78 in premarket trading.

"We have concluded that two independent companies focused on their respective industries will be better positioned to pursue their individually focused business strategies," Mulva said in a statement.

Conoco's announcement comes on the heels of the breakup of Marathon Oil first announced in January. On July 1, Marathon Petroleum Corp., the refining company, began trading on the New York Stock Exchange under the "MPC" ticker symbol. Marathon Oil Corp. kept its ticker symbol of "MRO."

Conoco said its board has approved separating its refining and marketing and exploration and production businesses by spinning off the refining and marketing segment to shareholders in a tax-free transaction.

The split, which is expected to be completed during the first half of next year, will leave Conoco as an exploration and production company.

Mulva will lead the separation efforts, but plans to retire once the split is complete.

Conoco said its separation plans do not require a shareholder vote. It expects to provide further details on the transaction "as they are determined over the next several months."

The Houston-based company has about 29,600 employees. Conoco had $160 billion of assets and $226 billion of annualized revenue as of March 31.