(Recasts with production restart, adds details)

By Catherine Bremer and Robin Emmott

MEXICO CITY, Aug 23 (Reuters) - World No. 5 oil exporter Mexico restarted its Gulf crude and gas production on Thursday and suffered only minor damage from ferocious Hurricane Dean, state energy monopoly Pemex said.

Pemex, a major supplier to the United States, said it produced 342,000 barrels of crude in Campeche Bay on Thursday and aimed to get oil production back up to normal levels "in the next few days".

Pemex shut down 2.65 million bpd of production when Dean hit Mexico.

The company -- already affected this year by declining yields at its huge but aging Cantarell oil field in the Mexican Gulf -- planned to have its 18,000 Gulf workers back at their posts by Friday.

"A few hours ago, (Pemex) restarted its crude and gas production in the Bay of Campeche after having concluded an aerial and physical revision of a large part of the deep sea rigs, which showed there were no great damages," Pemex said in a statement.

Two of Mexico's three main oil shipping ports reopened on Thursday, after all three were shut as Dean raced through the Gulf of Mexico on Tuesday. Pemex halted oil shipments from two ports as early as Monday.

Port supervisor Arturo de la Cruz told Reuters the key Dos Bocas oil port was operating normally, while another port official said the first of several crude oil tankers had left Pajaritos, part of the Coatzacoalcos port complex.

Mexico's third main Gulf of Mexico oil port, Cayo Arcas, remained closed on Thursday evening, however, according to a transport ministry statement. "There is no movement there," a port official told Reuters earlier in the day.

In normal conditions, Pemex exports some 1.7 million barrels per day of crude oil. Around 80 percent of that goes to the United States, mostly leaving from Dos Bocas, Pajaritos and Cayo Arcas, and the rest from the Pacific coast.

MONSTER STORM

Pemex shut down production when Dean -- a monster Category 5 storm as it smashed into Mexico's Caribbean coast Tuesday -- raced westward across the Yucatan Peninsula and raged into the Mexican Gulf.

The company said on Thursday its six oil refineries had not been affected by the hurricane and all were operating.

"They are operating normally, production levels are normal," a spokeswoman said, brushing off talk in gasoline markets that runs at the Cadereyta refinery in the northern state of Nuevo Leon were down by 25 percent.

An employee at the Minatitlan refinery, which is on the southern Gulf of Mexico coast and was the only refinery located close to the path of the hurricane, confirmed the plant had not been hit hard by Dean and was operating as normal.

(Additional reporting by Cyntia Barrera Diaz)

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