McLEAN, Virginia (AP) ― The United States accused Syrian President Bashar Assad’s government of using an American citizen to spy on anti-Syrian protesters in the U.S., an accusation that further strains relations between Washington and Damascus, which has unleashed a brutal crackdown on dissidents that has killed thousands.

Mohamad Anas Haitham Soueid, 47, of Leesburg, Virginia, a Syrian-born, naturalized U.S. citizen, is accused of sending audio and video recordings of American protesters to Syria’s intelligence agency and traveling to Syria to meet with Assad.

The Syrian Embassy issued a statement strongly denying that Soueid was an agent for the government or that he personally met with Assad. It called the accusation “absolutely baseless and totally unacceptable.”

International pressure is building on Assad to step down over his regime’s bloody crackdown on anti-government protests that the U.N. says has left nearly 3,000 people dead. Earlier Wednesday, tens of thousands of Syrians gathered in Damascus to show their support for Assad, though opponents claim such rallies are staged by his regime.

Activists say Soueid’s indictment reflects one aspect of a crackdown on the popular revolt in Syria that extends well beyond the country’s borders. In June, Britain’s Foreign Office summoned Syria’s ambassador amid reports that a diplomat had been intimidating Syrian protesters in the UK.

An Amnesty International report issued on Oct. 3 said protesters outside Syria have been systematically monitored and harassed by embassy officials and others believed to be acting on behalf of the Syrian regime.

“The mentality of the Syrian regime is to track all the dissidents and know what they’re doing,” said Ahed al-Hendi, a Syrian dissident who arrived in the United States as a political refugee and helped coordinate demonstrations in Washington.

Soueid was arrested Tuesday and charged with acting in the U.S. as an unregistered agent of a foreign government, according to an indictment unsealed Wednesday.

According to the indictment, Soueid sent 20 audio and video recordings between April and June to Syria’s intelligence agency, the Mukhabarat.

The indictment also states he traveled to Syria in June to meet with Assad personally. He was searched and questioned by authorities upon his return to Washington Dulles International Airport. Soueid informed his handler that he would have to change his procedures in the future as a result of the scrutiny, but that the he would continue his work on the “project.”

Prosecutors claim he also tried to recruit others to monitor anti-Assad rallies and protests in the U.S.

A federal magistrate ordered Soueid held Wednesday pending a detention hearing Friday after prosecutor Dennis Fitzpatrick said Soueid represents “a serious risk of flight.” He faces up to 40 years in prison if convicted on all six counts.

Soueid, dressed in a black fleece pullover and blue jeans, said he had not yet had a chance to contact his attorney, but did not say who his attorney is. Court records do not list one. Soueid had worked in the past as a manager at an import auto dealership, according to former colleagues.

Soueid earlier was named as a defendant in a lawsuit filed by anti-Assad activists against multiple government officials, including Assad.

That lawsuit claims that through Soueid’s efforts, “the (Assad) regime learns the identities of Syrians based in the United States, who are trying to assist in the efforts to counteract the tactics of the (Assad) regime. He transmits such information to Damascus to initiate criminal conduct against the families of the identified Syrians.”

Plaintiffs’ lawyer Martin McMahon said one of the plaintiffs had her father murdered by the regime and her home in Syria burned down. After the lawsuit was filed, she said her 5-year-old daughter in Syria was kidnapped, though eventually returned safely.

“Those people over there, they really play rough,” McMahon said.

Al-Hendi, the Syrian dissident, is also a plaintiff in the suit. He said protesters at multiple rallies noticed a man who arrived in a Hummer and snapped pictures of the crowd. Demonstrators assumed that pictures were not being taken for innocent purposes, he said.

Syria’s embassy in Washington called the allegations “lies and distortions.”

“These preposterous allegations claim that the embassy is involved in targeting or intimidating Syrian expatriates in the U.S., which is absolutely untrue,” it said in a statement commenting on the Amnesty report.