By Tom Bergin

LONDON (Reuters) - Royal Dutch Shell Plc beat all analyst forecasts by reporting an 18 percent jump in third-quarter profits thanks to higher oil and gas prices, setting a trend for the sector.

Europe's largest oil company by market value said current cost of supply (CCS) net income was $3.52 billion in the period.

Stripping out non-cash charges and one-off items, the result soared 88 percent to $4.93 billion, well ahead of an average forecast of $4.29 billion from a Reuters poll of nine analysts.

ConocoPhillips, the third-largest U.S. oil company, said on Wednesday that its quarterly profit more than doubled.

Both companies were helped by a 12 percent rise in crude prices compared to the third quarter of 2009, while U.S. natural gas prices were 29 percent higher and British gas prices doubled. Average global refining margins also rose.

Industry leader Exxon Mobil is due to report its third-quarter results later on Thursday and analysts have forecast a 53 percent rise in net income to $7.26 billion.

Shell also contributed to its rebound, with a 5 percent rise in oil and gas production in the quarter compared to the same period of 2009, to 3.1 million barrels of oil equivalent per day (boepd), just ahead of forecasts.

However, the main outperformance versus expectations was in Shell's refining unit, where underlying profits were around 50 percent higher than analysts predicted.

Chief Executive Peter Voser said Shell would continue to sell non-core assets, especially in retail and refining, and promised a "rationalization" of the Anglo-Dutch company's U.S. tight gas assets in North America.

(Reporting by Tom Bergin; Editing by Michael Shields)