Turkish authorities have detained at least 10 foreign nationals suspected of ties to a U.S.-based cleric whom Turkey accuses of masterminding the July 15 failed coup, a senior official said Monday.

At least four of them had been formally arrested pending trial while a fifth person had been released, Deputy Prime Minister Numan Kurtulmus told reporters after a Cabinet meeting. One of the suspects was detained on Saturday after entering Turkey illegally from Syria, the deputy premier said. Kurtulmus said at least one wanted foreign national was on the run.

He didn't provide details on their nationalities, but said the number of foreigners detained could increase as the investigation deepens.

Turkey's government launched a sweeping crackdown targeting followers of U.S.-based Muslim cleric Fethullah Gulen, who is accused of behind the coup attempt by renegade soldiers within the military. Gulen, who lives in self-imposed exile in Pennsylvania, has denied involvement.

Nearly 18,000 people have been detained or arrested in the crackdown, mostly from the military. Tens of thousands of people have been suspended or dismissed from jobs in the judiciary, media, education, health care, military and local government.

The scope of the crackdown has alarmed European countries and rights groups, who have urged restraint, triggering criticism by President Recep Tayyip Erdogan who has angrily complained of a lack of support from Turkey's allies.

The government is demanding Gulen's extradition from the U.S. Washington has said it would need evidence of the cleric's involvement, and says the extradition process must be allowed to take its course.

On Sunday, Turkey held a mass rally in Istanbul to denounce the attempted coup, which two main opposition party leaders attended in a show of unity.

Kurtulmus, citing police figures, said as many as 5 million people had attended the rally, which he described as a strong expression by the Turkish people of their demand that Gulen be returned to Turkey to face trial. Turkey also is pressing for the extradition of other U.S.-based Gulen supporters.

"I have no doubt that U.S. officials will review their stance (on Gulen)," Kurtulmus said. "Either they will continue to protect three or five bandits, or they will act in a way that will allow them to win the hearts of a nation of 79 million people."

Kurtulmus said the government doesn't believe Gulen's movement would be capable of staging another military coup, but didn't rule out possible acts of sabotage by his followers, including cyberattacks. Kurtulmus said, however, that Turkey was taking measures to counter any possible threat.

"I can confidently say that there is no longer a threat of (another) coup," Kurtulmus said. "But this organization will continue ... to take action to harm Turkey."

The deputy premier reiterated that 216 military personnel -- including nine generals -- suspected of taking part in the coup were at large. Of the fugitives, 180 of them were army personnel while 30 were paramilitary police. He wouldn't confirm Turkish media reports that claimed that some of the officers may have found refuge with Kurdish rebels in northern Iraq, dismissing the reports as "speculation."

Also Monday, Kurtulmus announced that the government had lifted a decision to cancel all civil servants' leaves which had forced many to return from vacations or cancel travel plans. The ban was imposed soon after the coup attempt to allow authorities to investigate officials' possible links to the Gulen movement.