RIYADH, April 28 (Reuters) - The arrest of 172 suspected militants did not end the al Qaeda-linked threat in Saudi Arabia, the interior minister was quoted as saying on Saturday, vowing to maintain a crack down on the group.

Prince Nayef also told the Arabic-language al-Riyadh daily that a Saudi man was being held on suspicion of leading one of the seven cells which had been smashed, foiling a plot to attack oil facilities and military bases.

"We cannot say that we are finished from these deviants," said Prince Nayef. "But efforts will continue. The eyes ... are wide open and efforts are under way to purify our country from every evil," he added.

The Interior Ministry said on Friday it foiled an al Qaeda-linked plot to attack oil facilities, military bases and public figures in western-allied Saudi Arabia, arresting a total of 172 people, including some who had trained to use aircraft for suicide attacks.

It said police also seized weapons, computers and more than 20 million riyals ($5 million) in cash.

Islamist militants swearing allegiance to al Qaeda launched a violent campaign to topple the U.S.-allied Saudi monarchy in 2003, carrying out suicide bomb attacks on foreigners and government installations, including the oil industry.

Saudi Arabia is the world's top oil exporter, supplying about 7 million barrels a day to world markets. It holds nearly a quarter of the world's oil reserves.

Most of the 19 al Qaeda militants who commandeered hijacked planes in the Sept. 11 attack on the United States were Saudis.

Prince Nayef said Riyadh was also holding a Saudi man believed to be the leader of one of the broken cells, after members swore allegiance to him at the Kaaba, a sacred site inside the Grand Mosque in Mecca, Islam's holiest city.

"Unfortunately, he is a Saudi. He was arrested along with the group," he said, without giving further details.

Asked if the man was the leader of the group, he said: "If this man looks at himself as such, we are not sure. But no one pledges allegiance to someone unless he himself has presented himself as a leader and has followers."

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