Updates shares in paragraph 2, adds background and graphic

May 5 (Reuters) - Marathon Petroleum MPC.N on Tuesday beat Wall Street estimates for first-quarter profit, benefiting from stronger refining margins amid tighter global supply driven by the Middle East war.

Its shares rose 2.8% in early trading, with the stock up 60% so far this year.

The company approved an additional $5 billion share repurchase program, bringing the total remaining authorization to about $8.6 billion.

U.S. refined products exports hit a record high in March as the Iran war and the near-closure of the Strait of Hormuz tightened global fuel supplies, forcing output cuts abroad and supporting margins for U.S. refiners, which are less reliant on Middle Eastern crude and are well placed to capture demand through exports.

Marathon Petroleum, the top U.S. refiner by volume, said refining and marketing margin was $17.74 per barrel for the first quarter, 32.6% higher than last year.

The strong margins have lifted results across the sector, with Valero Energy VLO.N, Phillips 66 PSX.N and HF Sinclair DINO.N all reporting profits that exceeded expectations.

Marathon reported crude capacity utilization of 89%, resulting in total throughput of 2.9 million barrels per day (bpd) in the first quarter, compared with 2.8 million bpd a year earlier.

For the second quarter, Marathon expects throughput of 2.99 million bpd.

First-quarter results were partly offset by higher operating costs linked to refinery turnaround activity and derivative losses tied to economic hedging.

It expects to spend $1.5 billion in 2026, largely on projects to improve margins at key refineries.

In the first quarter, Marathon brought its Garyville jet flexibility project online, enabling it to upgrade existing output into higher-value jet fuel and capture rising domestic and export demand.

The Findlay, Ohio-based refiner reported adjusted profit of $1.65 per share for the quarter ended March 31, beating analysts' average estimate of 75 cents per share, according to data compiled by LSEG.